Cu-based composites with multiscale configuration for electrical contact applications are fabricated via a ball milling (BM)-spark plasma sintering (SPS)-aging process. Synergistic strengthening of the Cu alloy matrix by micro-scale metallic glass particles and nanoscale intracrystalline precipitation phases is realized. The annealing technique achieves the decomposition of solute atoms in the Cu alloy, ensuring the excellent electrical properties of the matrix conductive network. The composite with multiscale configuration achieves an outstanding combination of ultimate compressive strength of (1114 ± 15) MPa and electrical conductivity of 33.0% ± 1.1% International Annealed Copper Standard (IACS) after annealing at 400 °C for 10.0 h. Investigation of the strengthening and conductivity mechanisms suggests that the precipitation of the Cr-rich phase within the matrix crystals is a critical contributor to the concerted enhancement of strength and conductivity. In addition, the positive role of nanocrystals precipitated at the edges of metallic glass particles on the interfacial bonding of composites is addressed. Graphical abstract: [Figure not available: see fulltext.]

Structural features of the Pd42.5Cu30Ni7.5P20 and Pt42.5Cu27Ni9.5P21 metallic glasses are studied in the present work by high-resolution transmission electron microscopy. The results indicate that Pd42.5Cu30Ni7.5P20 is a true bulk glass-former containing no crystalline particles/nuclei, while Pt42.5Cu27Ni9.5P21 is a crystal growth-controlled type bulk glass-former which contains nanoparticles of about 1 nm size with a different chemical composition. These structural differences are manifested in room-temperature mechanical properties. Thermodynamic calculations are also used to support the observed features.

Magnetic semiconductors with Curie temperatures higher than room temperature show potential for developing spintronic devices with combined data processing and storage functions for next-generation computing systems. In this study, we present an n-type Co19.8Fe8.6Nb4.3B6.0O61.3 magnetic semiconductor with a high Curie temperature of ∼559 K. This magnetic semiconductor has a room-temperature resistivity of ∼2.10 × 104 Å cm and a saturation magnetization of ∼76 emu/cm3. The n-type Co19.8Fe8.6Nb4.3B6.0O61.3 magnetic semiconductor was deposited on p-type silicon to form a heterojunction, exhibiting a rectifying characteristic. Our results provide the design principles for discovering high Curie temperature magnetic semiconductors with determined conduction types, which would play an essential role in realizing nonvolatile spin-based transistors that break free from the confines of currently established Si-based information technology.

In current paper we present a new additive manufacturing method of production of bulk/macroscopic double-layer metallic materials by a unique Double Spray Forming machine in situ under a protective high-purity argon atmosphere. This method allows direct layer by layer deposition of metallic materials with good interlayer adhesion without formation of internal oxides. The double-layered materials including metal 1/metal 2, crystalline alloy 1/crystalline alloy 2 and crystalline alloy/glassy (amorphous) alloy were produced. The resulting materials consist of a combination of a relatively hard layer 1 and a relatively soft layer 2, thus making an in-situ layered composite “inlaycom”. The obtained structures were examined by X-ray diffractometry and scanning electron microscopy. The paper is focused to show the principle of the process usable as a scientific instrument. The proposed method can be applied for production of other double layer metallic materials including crystal/glassy ones and can be used by the scientists and engineers working in various research fields.

The present review is related to the studies of structural changes observed in metallic glass-forming liquids on cooling and subsequent vitrification in terms of radial distribution function and its analogues. These structural changes are discussed in relationship with liquid’s properties, especially the relaxation time and viscosity. These changes are found to be directly responsible for liquid fragility: deviation of the temperature dependence of viscosity of a supercooled liquid from the Arrhenius equation through modification of the activation energy for viscous flow. Further studies of this phenomenon are necessary to provide direct mathematical correlation between the atomic structure and properties.

Creation of FeNi-based hard magnetic materials for a high-density recording media depends on many factors including chemistry, synthesis conditions and subsequent heat-treatments. In particular Fe-Ni thin films can be fabricated by sputtering, molecular beam epitaxy and electrodeposition. The highest values of anisotropy constant are obtained for ordered tP4/L10-FeNi compound. From the viewpoint of practical use, a challenging task is to propose the relevant technological schemes for fabrication of this compound. This work is devoted to a study of three types of materials produced by radio frequency magnetron sputtering: layered Fe/(Ni,Pt) crystalline samples deposited at room temperature and subsequently annealed, homogeneous crystalline Fe(Ni,Pt) samples deposited at elevated substrate temperature and amorphous Fe-Ni-Pt-Zr samples deposited at room temperature which were further crystallized on heating. The phase composition of the sample was studied by X-ray diffractometry while the obtained nanostructure was observed by transmission electron microscopy. Thermally crystallized Fe-Ni-Pt-Zr samples exhibited the best combination of magnetic properties among the deposited films though partial oxidation of the samples took place on sputtering and annealing. Chemical composition and microstructure features, namely grain structure and defects in the Fe(Ni,Pt) samples are proposed to be main reasons responsible for the observed magnetic properties.

A metallic glass of nominal composition Mg75Ni20Mm5 (Mm: mischmetal) when heated shows primary crystallization to Mg2Ni. Transmission electron microscopy studies, including annealing experiments in-situ, supported by differential scanning calorimetry and X-ray diffraction, reveal the remarkable complexity of this crystallization. The crystals are lens-shaped and at constant temperature show linear (constant-rate) growth, despite marked partitioning of nickel from the glass to the crystal. The growth, constrained by atomic rearrangement at the glass-crystal interface, gives a crystalline phase that is partially disordered and has almost half of its magnesium sites vacant. The combination of solute partitioning and isothermal linear growth challenges usual assumptions about the characteristics of primary and polymorphic crystallization. This hybrid behavior is interpreted in terms of the widely differing diffusivities of the atomic species in this system.

Amorphous bulk metallic glasses with the composition Fe48Cr15Mo14C15B6Y2 have been of interest due to their special mechanical and electronic properties, including corrosion resistance, high yield-strength, large elasticity, catalytic performance, and soft ferromagnetism. Here, we apply a reverse Monte Carlo technique to unravel the atomic structure of these glasses. The pair-distribution functions for various atomic pairs are computed based on the high-energy x-ray diffraction data we have taken from an amorphous sample. Monte Carlo cycles are used to move the atomic positions until the model reproduces the experimental pair-distribution function. The resulting fitted model is consistent with our ab initio simulations of the metallic glass. Our study contributes to the understanding of functional properties of Fe-based bulk metallic glasses driven by disorder effects.

The glass formation ability of an alloy depends on two competing processes: glass-transition on one hand, crystal nucleation and growth on the other hand. While these phenomena have been widely studied before in nearly equiatomic Cu-Zr alloys, studies are lacking for solute/solvent-rich ones. In the present work, molecular dynamics simulations show that the addition of a small amount of Zr (1-10 at. %) to Cu drastically increases incubation time and slows down crystal growth, thus leading to an improved glass forming ability. The crystal nucleation and growth processes of a competing face-centered cubic (FCC) Cu crystalline phase are analyzed in detail. In particular, the values of critical cooling rate, incubation period for crystallization and growth rate of FCC Cu crystals in these Cu-rich alloys are obtained. The growth of a supersaturated FCC Cu solid solution is found to be polymorphic at the interface (except for alloys with 9 and 10 at. % Zr) though a Zr concentration gradient is observed within growing crystals at high enough Zr content. The crystal growth rate before crystal impingement is nearly constant in all alloys, though it decreases exponentially with Zr content. Crystallization kinetics are also analyzed within the existing theories and compared with the experimental values available in the literature.

Deformation of a Cu-Pd-P amorphous alloy is studied under periodical mechanical load (stress/unload cycle with 0.3 Hz or 3 Hz frequency) on heating at the constant rate of 5 K/min. We show that deformation of the material is interpolated with a hyperbolic function of time or temperature. As predicted non-isothermal cyclic deformation takes place with wave effects, which are a result of the combination of heating and cyclic mechanical loading. A reaction force graph of alloy was analysed as a surface with two variable parameters: loading frequency and time. The proposed model describes the resonance processes from the standpoint of non-linear dynamical systems.

Low temperature relaxation and structural changes in a Cu36Zr48Al8Ag8 bulk glassy alloy well below the glass-transition temperature are examined by using differential scanning calorimetry, X-ray diffractometry, scanning and transmission electron microscopy. Although densification of the sample takes place owing to beginning of structural relaxation both room-temperature mechanical strength and plasticity values are increased. The studied samples exhibited an inverse relationship between compressive strength and hardness. However, no clear structural changes in terms of crystallization or phase separation are observed. The results are interpreted in terms of both structural relaxation and release of internal stresses.

Recently, nanocrystalline Ti-Ni-Cu-Co system alloys were found to have excellent stability of superelastic behaviour for elastocaloric applications. One of the factors limiting implementation of TiNi-based alloys in microelectromechanical systems is residual elastic stresses. In this work, the structure formation and stress evolution in the Ti50Ni22Cu22Co6 glassy/crystalline ribbon are studied on heating. The as-cast alloy has a glassy structure in the middle part of the ribbon while the surface crystals of textured B2 phase are found. However, due to the sharp [100] texture and B2 phase stabilizing effect, the only partial recrystallization takes place on subsequent heating. The x-ray diffraction studies indicated that the elastic stresses in the B2 phase reach a value of ~750 MPa near the surface plane. After isothermal annealing at crystallization temperature, the level of residual stresses reduced by a factor of 2. The origin of elastic stresses induced in the glassy/crystalline matrix is discussed.

We utilise displacement analysis of Cu-atoms between the chemical bond-centred Voronoi polyhedrons to reveal structural changes at the glass transition. We confirm that the disordered congruent bond lattice of Cu loses its rigidity above the glass transition temperature (Tg ) in line with Kantor–Webman theorem due to percolation via configurons (broken Cu-Cu chemical bonds). We reveal that the amorphous Cu has the Tg = 794 ± 10 K at the cooling rate q = 1 × 1013 K/s and that the determination of Tg based on analysis of first sharp diffraction minimum (FDSM) is sharper compared with classical Wendt–Abraham empirical criterion.

Abstract: The alloys without a base component (also called high-entropy alloys) with good mechanical properties can be obtained not only by compositional optimization starting from the equiatomic mixture but by dilution of the base component (Fe) in a commercial industrial steel by another transition metal. Low density Fe–Mn–Al–C system alloys containing up to 30 mass% of Mn and up to 10 mass% of Al is an excellent base system for utilizing the latter approach. In this article, we present a Fe–Mn-Co–Al–C alloy with good tensile plasticity of 10% and an extremely high yield and ultimate strength values up to 1590 and 1650 MPa, respectively, treated only by standard technological operations: homogenization, hot and cold rolling and annealing. This is achieved by exploring the high-entropy approach forming a duplex-type solid-solution structure without dispersion strengthening with carbide precipitates. Mechanical strengthening is a result of solid-solution hardening and deformation strengthening upon the applied thermomechanical treatments. This approach also can be applied to other various alloys. Impact statement: Constant scientifc and technological progress requires the creation of new structural materials with enhanced properties. In addition, the next generation of commercial aircrafts and vehicles requires materials with a higher specifc strength to meet fuel emission requirements. However, research on conventional metallic alloys has reached a saturation point, requiring the development of new scientifc ideas to ensure further progress in this area of materials science. A recent promising invention is related to high-entropy alloys: alloys without a main component. A typical group of high entropy alloys is an equiatomic mixture of several 3d transition metals. However, one can approach the equiatomic composition by starting with an existing alloy composition by diluting the base metal component with a related metal. We propose using a lightweight Fe-Mn-Al-C steel with high Mn and Al content as an excellent base system. High-entropy alloys containing cF4 and cI2/cP2 crystalline phases are obtained in this work by diluting the main component (Fe) in the industrial Fe–Mn–Al–C steel with another 3d transition metal (Co). One of the obtained alloys showed mechanical properties superior to those of the base alloy. This approach can also be applied to various other industrial alloys in the future. Graphic abstract: [Figure not available: see fulltext.]

The paper analyzes the effect of severe plastic deformation on the structure, mechanical and thermal properties of a Zr42.5Сu42.5Al10Fe5 alloy. It was found that high pressure torsion induces phase separation of an amorphous matrix and causes formation of a complex structure containing nanocrystalline particles. The precipitation of nanocrystals leads to a change in the composition of the amorphous matrix and changes in the crystallization process and characteristic temperatures of the alloy. It is shown in the work that high pressure torsion significantly increases the hardness of the material, which is associated with the formation of nanocrystals in the structure and elastic stresses.

Samples of two kinds of bulk metallic glasses (BMG) with different compositions, Zr48Cu36Al8Ag8 and Zr57Cu15.4Al10Ni12.6Nb5, were polished to mirror-like quality and, after measuring the initial reflectance at normal light incidence, were subjected to impact of ions of deuterium or argon plasma with fixed energy. The main attention was paid to phenomenon on deuterium absorption that reveals as the weight gain after every exposure of the samples in deuterium plasma. For a fixed ion energy (in the range<100 eV), the amount of absorbed deuterium increased linearly with increasing of the ion fluence. Bending of the samples was observed when one side of sample was bombarded by deuterium plasma ions. At that, the radius of curvature of samples was decreasing with increasing the amount of trapped deuterium in such a way that its curvature was increasing proportionally to the amount of trapped deuterium. This is an evidence of near-surface distribution of the trapped deuterium. The results demonstrate that D ions within a fluence of ∼2·1025 ions/m2 are initially accumulated in a thin near-surface layer of the samples. Further, they are noted effects of stress relaxation and of deuterium redistribution.

Shear-induced segregation, by particle size, is known in the flow of colloids and granular media, but is unexpected at the atomic level in the deformation of solid materials, especially at room temperature. In nanoscale wear tests of an Fe-based bulk metallic glass at room temperature, without significant surface heating, we find that intense shear localization under a scanned indenter tip can induce strong segregation of a dilute large-atom solute (Y) to planar regions that then crystallize as a Y-rich solid solution. There is stiffening of the material, and the underlying chemical and structural effects are characterized by transmission electron microscopy. The key influence of the soft Fe–Y interatomic interaction is investigated by ab-initio calculation. The driving force for the induced segregation, and its mechanisms, are considered by comparison with effects in other sheared media.

Abstract: This work investigates the effect of chemical composition on the microstructure and properties of cast high-entropy alloys, and optimal conditions for homogenization annealing. The investigation is performed on alloys of the following compositions: Fe22.5Ni22.5Cu22.5Co22.5Al10, Fe22.5Ni22.5Cu22.5Cr22.5Al10, and Fe22.5Ni22.5Cu22.5Mn22.5Al10 (shortly Fe22.5Ni22.5Cu22.5(Co, Cr or Mn)22.5Al10), melted in an induction furnace with casting into a copper mold. The structural and phase changes in high-entropy alloys of different chemical composition are examined before and after homogenization annealing. The morphology of crystalline phases and microstructural evolution are analyzed experimentally. The strength characteristics of the alloys subjected to different homogenization annealing conditions are determined.

In the present work we study crystallization of the Ti50Ni22Cu22TM6 (TM stands for other transition metals: Cr, Mn and Fe) glassy alloys produced by rapid solidification of the melt. The effect of the additional transition metals Cr, Mn and Fe in stabilization of a cP2/B2 type phase is clarified in comparison with the base ternary Ti50Ni25Cu25 alloy. The transformation temperature and heat effects were studied by differential scanning calorimetry. The structure of the samples in the as-prepared and annealed states was examined by X-ray diffraction and transmission electron microscopy. Polymorphic transformation mechanism leading to the formation of the cP2/B2 type phase is studied in detail. Crystal nucleation and growth initiate on the free surface of the Fe-bearing alloy leading to the strong< 100 >texture formation and weak exothermic reaction which changes the shape of the DSC curves. On the contrary, the crystallization occurs within the entire volume of the Mn- and Cr-containing samples, indicating the effect of nucleation and growth of pre-existed nuclei in the glassy state on the heat release of crystallization and the resulted microstructure.

The article analyzes the effect of the addition of iron in the Zr–Cu–Al system metallic glassy alloys on the phase separation process during thermo-mechanical treatment. The addition of Fe causes formation of nanostructured regions of chemical inhomogeneity after cold rolling and annealing below the glass transition temperature. The resulted effect on the mechanical properties of the investigated alloys is established. Changes in the structure during thermo-mechanical treatment are studied in detail by transmission electron microscopy. The increase in the microhardness of the alloys during the formation of inhomogeneities in the amorphous matrix is explained by the difficulty of propagation of the shear bands formed during deformation.

An Erratum to this paper has been published: https://doi.org/10.3103/S1067821221040155.

The specific features of B2 atomic ordering and the ordering-dependent structure and magnetic characteristics of the FeCo alloy upon quasi-hydrostatic high-pressure torsion (HPT) in the Bridgman anvils at room and elevated temperatures and subsequent annealing have been studied by thermal neutron diffraction, X-ray diffraction, EXAFS spectroscopy, and magnetometry. An abrupt decrease in the degree of long-range order upon HPT has been revealed by neutron diffraction and EXAFS spectroscopy data exhibiting the formation of an almost ideal B2 ordering of in the nearest coordination spheres of Fe and Co atoms.

Modelling of the deformation process of Al85Y8Ni5Co2 amorphous alloys was carried out under simultaneous application of cyclic mechanical load (at 0.3 or 3 Hz frequencies) and continuously increasing temperature (heating rate 5 K/min). It is shown that deformation of the amorphous specimens occurs by the hyperbolic temporal dependence. It is analytically determined and experimentally proved that for non-isothermal cyclic deformation, the wave effects take place as a result of the superposition of thermal-activated and mechanical components. The behaviour of the material under thermo-mechanical action was described qualitatively within the framework of Spaepen’s model. The dependencies for the reaction force of the samples were obtained as two-parameter functions of the frequency and temperature. A reaction force surface of a specimen, as a function of the different forcing frequencies and time, has been plotted.

The mechanical characteristics and the operative deformation mechanisms of a metallic alloy can be optimised by explicitly controlling phase stability. Here an integrated thermoelastic and pseudoelastic model is presented to evaluate the β stability in Ti alloys. The energy landscape of β→α′/α″ martensitic transformation was expressed in terms of the dilatational and transformational strain energy, the Gibbs free energy change, the external mechanical work as well as the internal frictional resistance. To test the model, new alloys were developed by tailoring two base alloys, Ti–6Al–4V and Ti–6Al–7Nb, with the addition of β-stabilising element Mo. The alloys exhibited versatile mechanical behaviours with enhanced plasticity. Martensitic nucleation and growth was fundamentally dominated by the competition between elastic strain energy and chemical driving force, where the latter term tends to lower the transformational energy barrier. The model incorporates thermodynamics and micromechanics to quantitatively investigate the threshold energy for operating transformation-induced plasticity and further guides alloy design.

In TiNi-based crystalline/amorphous alloys, superelasticity in crystalline phase coordinating the dislocation sinking in amorphous phase lead to a high ductility and outstanding anti-fatigue properties. We performed cryogenic thermal cycling, between 77 K and 303 K, on the complex TiNi-based alloys consisting of a major B2 austenite phase, an interdendritic amorphous phase, and a minor B19′ martensite phase in the as-cast state. The critical martensitic phase transformation stress (σ ) increased with the number of thermal cycles, reaching a maximum at 10 cycles. The initial B19’ martensite which is confined in the amorphous phase transformed to B2 austenite due to thermal induced stable transformation. A lamellar structure of alternating amorphous and crystalline layers dominantly grew into the amorphous matrix as a consequence of the thermal fatigue during the cryogenic thermal cycling. Initial cell for the molecular dynamic simulations was carefully prepared to contain three different phases. Cyclic compressive loading and cryogenic thermal cycling simulations were consistent with the experimental results. m

The effect of cryogenic cycling treatment on the elastic properties of a Fe Cr Mo C B Y bulk metallic glass containing a nanometer scale native oxide film is studied in the present work using an atomic force microscope. The internal structure was characterized by transmission electron microscopy while the surface oxide layer was tested by X-ray photoemission spectroscopy. The alloy showed surface elastic stiffening on thermal cycling in liquid nitrogen which relaxed in 2 days. The obtained results are discussed in comparison with the bulk metallic glasses studied earlier. 48 15 14 15 6 2

Low plasticity is a key drawback limiting the widespread use of bulk metallic glasses. Although heat treatment and thermo-mechanical processing techniques are not applied to metallic glasses (only to supercooled liquids), since heating leads to embrittlement either due to structural relaxation or thermal crystallization, in this paper, we demonstrate a strong positive effect of cold rolling and subsequent thermal annealing below the glass-transition temperature on room-temperature mechanical properties of a Zr Cu Fe Al glassy alloy. As a result we observed mechanical softening and appearance of tensile ductility (up to 1.5%) in bulk samples and an increase in hardness by up to 25% in ribbon samples yet retaining good bending plasticity. We believe that the proposed method can be applied to a number of metallic glasses. 62 · 5 22 · 5 5 10

Reducing the deformation temperature is an important research task for superplastic forming of Ti-based alloys. This study demonstrates that the additions of Fe and B significantly improve microstructural homogeneity and superplastic performance, increase the post-forming mechanical strength, and reduce the superplastic deformation temperature of a Ti-Al-Mo-V alloy. The designed alloy exhibits an excellent superplastic deformation behavior with elongation of 590 to 1050 pct at 675 °C to 775 °C with a constant strain rate in a range of 5 × 10 to 5 × 10 s , and a high room temperature yield strength of 1020 MPa, a UTS of 1080 MPa, and elongation-to-failure of about 6 pct both after annealing and after superplastic deformation with a strain of 0.69 at 775 °C. The microstructure and the strain-induced changes in the size and shape of grains are discussed. The modification of the β-phase morphology leads to an increase in the curvature of interphase boundaries in the modified alloy. Advanced superplasticity and improved mechanical properties make the studied alloy a very attractive material for complex parts in numerous advanced applications.[Figure not available: see fulltext.] −4 −3 −1

High-pressure torsion allows one to achieve high strains of bulk metal glasses without their destruction. The article presents the results of studies on the effect of high-pressure torsion on the amorphous alloys of the same composition but obtained in different ways: in a form of a bulk plate and a melt-spun ribbon. It is shown that the degree of nonequilibrium after high-pressure torsion, determined by the diffraction and calorimetry methods, increases for bulk metallic glass, approaching the values characteristic for melt-spun alloy.

The quantitative characteristics of steps formed by shear bands (SB) on the surface of deformed samples of bulk amorphous Zr Ti Nb Cu Ni Al alloy were studied after high pressure torsion (HPT) and after rolling. It was found that the SB design depends on deformation mode. The deformation value decisively affects the SB power (the step height). 60 2 2 18.5 7.5 10

Structural relaxation, beta relaxation and crystallization processes of the Cu Y Al metallic glass were studied in the present work. X-ray diffractometry was used to study the structure of the samples. Phase transformations were studied by differential scanning calorimetry by using a power compensated type differential calorimeter. Cu-mould casting resulted in the formation of crystalline samples while fully glassy Cu Y Al alloy samples were produced by melt spinning at a high cooling rate of about 10 -10 K/s. This glassy alloy is characterized by strong beta relaxation and low activation energy values for crystallization and relaxation in comparison with other metallic glasses studied earlier. 53 42 5 53 42 5 5 6

The atomic structure variations on cooling, vitrification and crystallization processes in liquid metals face centered cubic (FCC) Cu are simulated in the present work in comparison with body centered cubic (BCC) Fe. The process is done on continuous cooling and isothermal annealing using a classical molecular-dynamics computer simulation procedure with an embedded-atom method potential at constant pressure. The structural changes are monitored with direct structure observation in the simulation cells containing from about 100 k to 1 M atoms. The crystallization process is analyzed under isothermal conditions by monitoring density and energy variation as a function of time. A common-neighbor cluster analysis is performed. The results of thermodynamic calculations on estimating the energy barrier for crystal nucleation and a critical nucleus size are compared with those obtained from simulation. The differences in crystallization of an FCC and a BCC metal are discussed.

The article analyzes the effect of the manganese addition on the thermal and electrical properties of the (ZrCu) Al Mn alloy where x=0; 0.5; 1; 2. The glassy alloy ribbons were produced by arc-melting and melt spinning technique. The structure of the samples was examined by X-ray diffractometry. The thermal properties were tested by differential scanning calorimetry. Four-point method was used to measure the electrical resistance. The addition of manganese significantly increases the resistivity of the alloys, as well as increases the strain sensitivity coefficient from 2.6 to 5.1. The obtained alloys are a potential substitute for alloys based on noble metals for use as a sensitive element of strain gauges. 90-x 10 x

Abstract: Multicomponent alloys without a base element, also known as highly entropic alloys (HEAs), are of great interest for research. The microstructure of the Fe20Ni20Co20Cu20Al20 alloy in a cast, annealed, and deformed state, as well as its mechanical properties and hot deformation ability, is investigated in this article. This alloy is a typical representative of the high-entropy alloy family. Samples are melted in a vacuum induction furnace in an argon atmosphere and then cast into a copper mold. Differential scanning calorimetry results are used to determine the solidus temperature. The homogenization annealing of cast samples is carried out in a high-temperature furnace in air. The microstructure of the alloy is studied by scanning electron microscopy and X-ray diffraction. X-ray microanalysis using X-ray energy dispersive spectroscopy is used to determine the chemical composition of the phases. It is shown that crystallization results in the formation of three solid solutions with one bcc and two fcc crystalline structures. The mechanical properties are investigated under uniaxial compression. Hardness is also measured. The deformation tests are carried out on a DIL805A/D quenching-deformation dilatometer and a Gleeble System 3800 complex for physical modeling and dynamic thermomechanical testing at temperatures of 900–1100°С and strain rates of 0.01–1.0 s–1 for a true degree of deformation of up to 1. Optimum modes of homogenization annealing for the typical representative of HEAs and optimal deformation modes are selected to obtain high mechanical properties.

In this work, the biomedical applicability and physical properties of magnesium-based metallic glass/polycaprolactone (PCL) composites are explored. The composites were fabricated via mechanical alloying and subsequent coextrusion. The coextrusion process was carried out at a temperature near to the supercooled liquid region of the metallic glass and the viscous region of the polymer. The structures, as well as thermal and mechanical properties of the obtained samples were characterized, and in vivo investigations were undertaken. The composite samples possess acceptable thermal and mechanical properties. Tensile tests indicate the ability of the composites to withstand more than 100% deformation. In vivo studies reveal that the composites are biologically compatible and could be promising for biomedical applications.

Structural changes in the Zr Cu Ni Al liquid alloy on cooling from above the equilibrium liquidus temperature are studied by synchrotron radiation X-ray diffraction and compared with the results of first-principles molecular dynamics simulation. In-situ vitrification of the studied alloy is achieved using a containerless levitation technique. Subsequent analysis of the atomic and electronic structure of the alloy in liquid and glassy states reveals formation of medium-range order on cooling and its relationship with liquid fragility. The structural changes in this alloy are smaller in comparison with a more fragile one. 55 30 5 10

High-strength crystalline/amorphous composites materials based on (Ti-Ni)-(Cu-Zr) system were developed. The optimal concentrations of additional alloying elements Al, Fe, and Cr were obtained. Structural investigations were carried out using X-ray diffraction equipment (XRD) and scanning electron microscope (SEM) with an energy-dispersive X-ray module (EDX). It was found that additives of aluminum and chromium up to 5 at% dissolve well into the solid matrix solution of the NiTi phase. At a concentration of 5 at%, the precipitation of the unfavorable NiTi phase occurs, which, as a result, leads to a dramatic decrease in ductility. Iron dissolves very well in the solid solution of the matrix phase due to chemical affinity with nickel. The addition of iron does not cause the precipitation of the NiTi phase in the concentration range of 0–8 at%, but with an increase in concentration, this leads to a decrease in the mechanical properties of the alloy. The mechanical behavior of alloys was studied in compression test conditions on a universal testing machine. The developed alloys have a good combination of strength and ductility due to their dual-phase structure. It was shown that additional alloying elements lead to a complete suppression of the martensitic transformation in the alloys. 2 2

Transformation of glasses into liquids is discussed in terms of configuron (broken chemical bond or transformation of an atom from one to another atomic shell) percolation theory with structural changes caused. The first sharp diffraction minimum (FSDM) in the pair distribution function (PDF) is shown to contain information on structural changes in amorphous materials at the glass transition temperature (T ). A method to determine the glass transition temperature is proposed based on allocating T to the temperature when a sharp kink in FSDM occurs. The method proposed is more sensitive compared with empirical criterion of Wendt-Abraham; e.g., for amorphous Ni the kink that determines T is almost twice sharper. Connection between the kink in fictive temperature behavior of PDF and Wendt-Abraham criterion is discussed. g g g

Scanning tunneling microscopy (STM) technique is widely used to study the electronic and structural properties of nano structures. Here we study the atomic structure of a Ni–Nb BMG by means of ultra high vacuum (UHV) STM in local areas of nanometer scale size, and report the direct atomic structure observation supported by ab initio molecular dynamics (MD) and density functional theory (DFT) simulations used to understand the observed structural and electronic features. It was possible to resolve the atomic surface structure of a bulk metallic glassy sample while MD simulation explained relatively large interatomic distances observed using STM.

Ti-based metallic glass (Ti-MG) short flakes were combined with Al7075 powder in order to form a Ti-MG-reinforced Al-based metal matrix composite (AMC) sintered by spark plasma sintering. The results show that the metallic glassy reinforcements maintained their amorphous structure and were uniformly distributed in the matrix. This microstructure results in a super-high strength of the composite with a compressive strength of more than 1 GPa. The high strength of the composite is mainly derived from the direct bearing of the metallic glass and the dislocation strengthening by the glassy reinforcement and the second precipitate phases. The present study shows that good bonding is one of the major advantage of metallic glass reinforced AMCs.

In the present paper we report on the magnetic properties of the (Fe0.7Co0.3)(83.7)Si4B8F3.6Cu0.7 ribbons produced by melt spinning and microwires prepared using Taylor-Ulitovsky technique. Depending on the cooling rate the ribbon samples have either an amorphous or partly crystalline structure. Excellent magnetic softness with coercivity of about 5 A/m and high saturation magnetization of about 1.87 T was found in the partly crystalline state ribbon. Glass-coated (Fe0.7Co0.3)(83.7)Si4B8F3.6Cu0.7 microwires with a mixed amorphous/nanocrystalline structure exhibit perfectly rectangular hysteresis loops and unusually high domain wall mobility that must be associated to elevated saturation magnetization values.

The effects of high pressure torsion at 77 and 295 K on the phase composition of soft magnetic alloys (FeCo)100-xVx (x = 0-6.0) were studied by X-ray structure analysis, transmission electron microscopy and magnetometry. It was established that HPT leads to the suppression of excess γ-phase in alloys containing 3.0-6.0% V. It was concluded that the observed effect was a consequence of the martensitic transformation γ→, due to deformation, along the lines of TRIP effect. It was established that suppression of the paramagnetic γ-phase leads to a noticeable increase in the specific magnetism of saturation.

Rising demand for bone implants has led to the focus on future alternatives of alloys with better biocompatibility and mechanical strength. Thus, this research is dedicated to the synthesis and investigation of new compositions for low-alloyed Ti-based compounds, which conjoin relatively acceptable mechanical properties and low elastic moduli. In this regard, the structural and mechanical properties of alpha + beta Ti-Fe-Cu-Sn alloys are described in the present paper. The alloys were fabricated by arc-melting and tilt-casting techniques which followed subsequent thermo-mechanical treatment aided by dual-axial forging and rolling procedures. The effect of the concentrations of the alloying elements, and other parameters, such as regimes of rolling and dual-axial forging operation, on the microstructure and mechanical properties were thoroughly investigated. The Ti94Fe1Cu1Sn4 alloy with the most promising mechanical properties was subjected to thermo-mechanical treatment. After a single rolling procedure at 750 degrees C, the alloy exhibited tensile strength and tensile plasticity of 1300 MPa and 6%, respectively, with an elastic modulus of 70 GPa. Such good tensile mechanical properties are explained by the optimal volume fraction balance between alpha and beta phases and the texture alignment obtained, providing superior alternatives in comparison to pure alpha- titanium alloys.

The effect of the degree of room-temperature plastic deformation by high-pressure torsion on the tendency to plastic flow in the Zr Cu Nb Ni Al Ti and Zr Cu Ni Al Ti bulk amorphous alloys has been studied by Vickers microindentation and precision measurements of the relative height of the “pileup” at the base of the indent. Three stages of the dependence of plasticity on the number of full revolutions of the moving anvil upon high pressure torsion of the alloys have been established. 60 18.5 2 7.5 10 2 52.5 17.9 14.6 10 5

Deformation-induced crystallization behavior of the Al85Y8Ni5Co2 metallic glassy samples subjected to cold and hot rolling with 35% size reduction is studied in the present work. The formation of primary nanoscale alpha-Al particles is observed after rolling at 473 K, which is below the glass-transition and crystallization temperature. It is found that contrary to thermal crystallization on heating below the glass-transition temperature, no intermetallic compounds but only alpha-Al nanoparticles were formed during the deformation-induced crystallization. The behavior is discussed in connection with the excess volume generated upon deformation. Structural changes are studied by x-ray diffractometry and transmission electron microscopy. Variation in the Vickers microhardness is also detected.

Thermal stability of different types of metallic glasses and partially crystalline alloys stored for at least 15 years at ambient conditions was tested in the present work by differential scanning calorimetry in comparison with that of the original alloys tested in the as-cast state in the earlier works. The structure of the naturally aged alloys was also studied by X-ray diffractometry. The structure of a couple of selected alloys was also tested by transmission electron microscopy. Most of the alloys retained their initial structure and showed only a moderate decrease in the crystallization temperature. Only those alloys which showed visible surface oxidation (Cu-Zr-system based) were partly transformed into a crystalline state forming micron-scale Cu particles in air at ambient conditions.

The microstructure and thermal and mechanical properties of (FeCoNiCuCr) -Nb multiprincipal-element alloys have been investigated in the as-cast and heat-treated state. The alloys were smelted by arc-melting in argon atmosphere. As-cast samples were produced by copper mold casting. The structure was studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis. The calculated phase diagrams of the Fe-Co-Ni-Cu-Cr-Nb system were used to predict the phase composition. The predicted thermodynamic temperatures and phase areas were compared with those obtained using differential scanning calorimetry (DSC) and the results of SEM observation, respectively. Addition of 10 at.% Nb caused phase separation of the alloy in the liquid state. Addition of Nb caused an increase in the yield strength by solid-solution hardening and by the formation of intermetallic compounds. Heat treatment also affected the mechanical properties of the studied alloys. 100−x x

Structural variation, vitrification, and crystallization processes in liquid nickel are simulated on continuous cooling and isothermal holding using a classical molecular-dynamics computer simulation procedure with an embedded-atom method potential at constant pressure. Structural changes are monitored with direct structure observation in the simulation cells, as well as by pair distribution and radial distribution functions created using the atomic coordinates. A cluster analysis is also performed. The crystallization kinetics is analyzed under isothermal conditions by monitoring density and energy variation as a function of time. As a result, a time-temperature-transformation diagram can be constructed over a wide temperature range.

Here we report on the structure and mechanical properties of low-alloyed Ti-based alloys containing Ag subjected to a dual-axial forging operation. The dependence of the microstructure and mechanical properties on the regimes of the dual-axial forging operation is studied for the Ti94Ag3Pd3 alloy having the optimal properties. The hemolytical activity of the Ti94Ag3Pd3 alloy was also investigated. The percent hemolysis induced by the sample after 5 h of incubation is much lower than that for the surgical titanium after 4 h of incubation. Doping of the Ti94Ag3Pd3 by a minor amount of nitrogen (N) improved its mechanical properties and decreased its elastic modulus (to 65 MPa), which is attractive for biological applications. (C) 2018 Elsevier B.V. All rights reserved.

Lack of plasticity is one of the main disadvantages of metallic glasses. One of the solutions to this problem can be composite materials. Diffusion bonding is promising for composite fabrication. In the present work the diffusion process in glassy multilayer films was investigated. A combination of advanced transmission electron microscopy (TEM)methods and precision sputtering techniques allows visualization and study of diffusion in amorphous metallic layers with high resolution. Multilayered films were obtained by radio frequency sputter deposition of Zr-Cu and Zr-Pd. The multilayers were annealed under a high vacuum (10−5 Pa)for 1 and 5 h at 400 °C, that is, well below the crystallization temperatures but very close to the glass-transition temperatures of both types of the glassy layer. The structural evolution in the deposited films was investigated by high-resolution transmission electron microscopy. It was observed that, despite the big differences in the atomic mass and size, Pd and Cu have similar diffusion coefficients. Surprisingly, 1 h of annealing results in formation of metastable copper nanocrystals in the Zr-Cu layers which, however, disappear after 5 h of annealing. This effect may be connected with nanovoid formation under a complex stress state evolving upon annealing, and is related to the exceptionally slow relaxation of the glassy layers sealed with a Ta overlayer.

The process of transition of the Zr55Cu30Al10Ni5 bulk amorphous alloy from an amorphous into a crystalline state has been investigated by using differential scanning calorimetry and dynamic mechanical analysis. The parameters of crystallization of the alloy, such as glass transition temperature (Tg), crystallization temperature (Tx), activation energy of crystallization (Ea), solidus and liquidus temperatures (Tsol, Tliq), crystallization enthalpy (ΔНх), melting heat (ΔHm) and solidification heat (ΔHsol) have been determined. The behavior of the storage modulus (EI), the loss factor (tan δ) with a temperature change from room temperature to 873 K has been studied. The phase structure of the alloy after crystallization was investigated by using X-ray diffraction.

The structural changes and mechanical properties of a Zr 63 Cu 22 Fe 5 Al 10 bulk metallic glass (BMG), and a Zr 63 Cu 27 Al 10 one made for comparison, were studied on annealing below the crystallization temperature. The phase composition of the samples was studied by conventional X-ray diffractometry and high-resolution transmission electron microscopy including the atomic-scale elemental mapping. The samples were mechanically tested in compression. The Zr 63 Cu 22 Fe 5 Al 10 bulk metallic glass shows a high strength and good deformability at room temperature both in the as-cast state and after prolonged structural relaxation below the crystallization temperature. The reasons for such behavior are discussed in the present work.

Fe-based metallic glasses (also called amorphous alloys) are known to have high hardness and high wear resistance. Here we study and present a Fe-Nb amorphous material with an unusual type of electrical conductivity behavior. The electrical transport properties of Fe-Nb oxide layers were studied by measuring local current-voltage characteristics by the atomic-force microscopy technique. At certain voltage levels the samples containing native oxides showed clearly asymmetrical conductivity relative to polarity of the applied potential. Fe-Nb metallic glassy surface oxide film growth process was monitored at ambient conditions. The growth rate keeps constant during the initial 2.5 hours. After that the growth rate drastically decreases and becomes almost zero while the final oxide thickness is 1.0–1.5 nm. The Fe-Nb film sample annealed for 15 minutes at 300 °C demonstrates several times larger oxide thickness and becomes an insulator. X-ray photoelectron spectroscopy was used to characterize the oxidation states in the surface amorphous oxides. This material can be readily applied as inexpensive nanoscale tunnel diode operating at the commonly utilized voltage of ±5 V.

The thermal and mechanical relaxation spectra of a Zr-Cu-Fe-Al bulk metallic glass were obtained before and after room-temperature cyclic loading up to 0.4% of elastic strain. The loading was performed using a dynamic mechanical analyzer at an oscillation frequency of 3 Hz to induce the structural changes within the glassy phase at room temperature. A double-stage structure relaxation behavior was monitored using the same dynamic mechanical analyzer at a lower strain on heating. These structure changes within the glassy phase were studied with X-ray diffractometry and high-resolution transmission electron microscopy. The cycling loading at room temperature lead to drastic changes in the atomic structure of the bulk metallic glassy samples. In particular, it caused partial nanocrystallization after 10,000 elastic cycles, which in turn influenced the relaxation behavior. The structural relaxation process of the Zr-Cu-Fe-Al bulk metallic glass monitored by thermal measurements is different from that observed by the dynamic mechanical analysis.

A composite material based on polyethylene terephthalate (PET, about 1% by mass) and Al85Y8Ni5Co2 metallic glass was obtained by mechanical alloying and consequent spark plasma sintering. The spark plasma sintering was performed at a temperature near to the super cooled liquid region of the metallic glass. Mechanical properties and the structural characterization of the composite material were obtained. It was conceived that composite samples (Al85Y8Ni5Co2/PET) have a better thermal conductivity in comparison with pure PET samples. The formation of the crystalline phases causes degradation of physical properties. It was calculated that the activation energy for crystallization of the Al(85)Ni(5)Y(8)Co(2 )metallic glass is higher than that of the other types of metallic glasses (Mg(67.5)Ca(5)Zn(27.5 )and Cu54Pd28P18) used for composite preparation previously. This denotes a good thermal stability of the chosen metallic glass.

© 2018 Elsevier B.V. We designed TiNi bulk metallic glass composite (BMGC) which has both a glassy phase and a crystalline phase. The TiNi BMGC undergoes a martensitic transformation during deformation, exhibits the superelastic behavior and excellent mechanical properties: strength of 2.5 GPa, ductility of more than 20%. It is known that mechanical-fatigue is an important feature which affects the martensitic transformation during superelastic cyclic loading. Comparison of the fatigue performances in TiNi dual-phase alloy and TiNi fully crystalline alloy demonstrates that the amorphous phase acts as the barrier and sinking of the dislocation slipping and promotes martensite-austenite phase transition during the superelastic cycling. The representative BMGCs provide a way to design metallic glasses with high ductility and outstanding anti-fatigue properties.

Room temperature deformation process in a bulk metallic glassy sample was studied by using a hydraulic thermomechanical simulator. The temperature rise during each separate shear band propagation event was measured with a high data acquisition frequency by a thermocouple welded to the sample. Calculation showed that when propagation of the well developed shear bands takes place along the entire sample the temperature inside the shear band should be close to the glass-transition temperature. It was also possible to resolve the temporal stress distribution and a double-stage character of stress drops was also observed. The obtained results are compared with the literature data obtained by infrared camera measurements and the results of finite elements modeling.

Surface state and its quality determine some important properties of metallic glasses. Control over of the nanoscale tribological behavior of metallic glasses is fundamental for their applications in micro- and nano-electromechanical devices. Owing to continuous miniaturization of these devices the mechanical contact area becomes of nanoscale, whereas the nanoscale wear resistance of metallic glasses can be improved taking into the account their surface oxides. Surface oxides also determine (bio)chemical properties of metallic glasses and alter their electrical properties. In the present paper we overview recent works on the subject and present the original research results related to the nanoscale tribological properties of metallic glasses.

The influence of cryothermal treatment on the mechanical properties of metallic glasses with different compositions was investigated in the present work. It was found that cryothermal cycling can induce rejuvenation as well as relaxation of the metallic glasses. The local apparent Young's modulus and its spatial distribution width on the surface of the metallic glass increase after cryothermal cycling, while in the bulk the effect depends on the glass composition. It appeared that this increase is temporary and disappears after a period of room temperature aging. This effect is connected with a large distribution of relaxation times in the metallic glasses due to their heterogeneous structure and the formation of complex native oxides on the outer surfaces of the glasses. Our findings reveal that a cryothermal cycling treatment can improve or degrade the plasticity of a metallic glass, and the atomic bond structure appears to be very important for the outcome of the treatment.

Crystallization of metallic glasses produced by rapid solidification and supercooled liquids on heating takes place at large undercooling which has some peculiarities compared to crystallization on casting. By using transmission electron microscopy we present a detailed in-situ study of an unusual isothermal crystallization reaction observed in the Al85Y8Ni5Co2 metallic glassy alloy below Tg. It started from the formation of a primary intermetallic compound (IMC) immediately followed by a pseudo-eutectic reaction consisting of IMC and nanoscale Al (solid solution) particles while α-Al particles are significantly smaller in size than the intermetallic phase. Moreover, a majority of these nanoscale α-Al particles do not have a common interface with the primary IMC particles but are separated by the residual glassy phase which remains present within these pseudo-eutectic colonies. On the other hand, as can be assumed from the Gaussian type of the heat flow plot at the isothermal conditions and reasonable linearity of the Avrami plot this reaction takes place like a single stage process. This residual glassy phase has a high stability versus crystallization and crystallizes only at a higher temperature. However, such a crystallization mechanism is observed only on slow heating or isothermal exposure at a temperature below Tg. On rapid heating or at isothermal annealing in the supercooled liquid, primary nanocrystallization of the aluminum solid solution is observed followed by the formation of intermetallic compounds at a higher temperature.

The following amendments are necessary: Page 552: The lattice parameters determined by the XRD for the FCC1 phase are 583.2 pm for the Al25Ti25Ni25Cu25 alloy, 582.3 pm for the Al22.5Ti22.5Ni20Cu20Fe15 alloy and 581.3 pm for the Al20Ti20Ni20Cu20Fe20 alloy. The lattice parameters determined by the XRD for the FCC2 phase are 365.4 and 364.7 pm for the Al22.5Ti22.5Ni20Cu20Fe15 and Al20Ti20Ni20Cu20Fe20 alloys, respectively. Page 553: Cooper should be Copper We sincerely apologize to the readers for any inconvenience it caused.

Ti-based alloys containing Pd, Au, and Nb were produced by tilt-casting and subsequently dual-axially forged at elevated temperatures. It is shown that the mechanical properties, electrochemical behavior and biocompatibility of the studied alloys are close to, or even better, than those of typical commercial Ti-based low-alloys widely used as biological implants. This demonstrates that the Ti94Pd3Au3, Ti94Pd3Nb3 and Ti94Pd6 alloys showed a good potential for application as biomaterials. (C) 2017 Elsevier B.V. All rights reserved.

Effect of multiple alloying elements on the glass-forming ability, thermal stability, and crystallization behavior of Zr-based glass-forming alloys were studied in the present work. We investigated the effect of complete or partial substitution of Ti and Ni with similar early and late transition metals, respectively, on the glass-forming ability and crystallization behavior of the Zr50Ti10Cu20Ni10Al10 alloy. Poor correlation was observed between different parameters indicating the glass-forming ability and the critical size of the obtained glassy samples. Importance of the width of the crystallization interval is emphasized. The kinetics of primary crystallization, i.e., the rate of nucleation and rate of growth of the nuclei of primary crystals is very different from that of the eutectic alloys. Thus, it is difficult to estimate the glass-forming ability only on the basis of the empirical parameters not taking into account the crystallization behavior and the crystallization interval.

The atomic-scale and nanoscale scratch wear resistance of a Cu47Zr45Al8 bulk metallic glass is studied in the present work using an atomic force microscopy focusing on the role of surface oxide and thermally induced changes in the glassy matrix. The wear rate is found to be significantly reduced and the wear resistance drastically improved by the formation of native and artificially grown surface oxides. This finding makes the studied alloy a very promising candidate for application as a wear resistant part in a micro-electro-mechanical device.

As well as the most of other 3d late transition metals Fe is a good β-Ti stabilizer, has a large solid solubility in β-Ti and owing to the atomic size difference with Ti can enable significant solution strengthening. The structure and mechanical properties of Ti alloys containing significant amount of Fe (or Fe together with Co, Cu and other elements) are reviewed in the present work. At high content of the late transition metals (for example, more than about 15 at% of Fe) the structure of these alloys consist of the rounded primary dendrites of an ordered cP2 intermetallic compound and an eutectic consisting of the cP2 intermetallic compound and a supersaturated cI2 β-Ti solid solution. cP2+cI2 phase TiFe alloys, their derivatives: TiFeCo, TiFeCu, etc+, and cI2 β-Ti solid solution alloys containing Sn and Nb exhibit high compressive strength and plasticity. At lower Fe content a supersaturated β-Ti solid solution single phase structure is formed. However, these alloys also show good mechanical properties especially when alloyed with Sn and Nb. The structure and properties of various kinds of such alloys are discussed in the present paper.

Shear bands play a key role in the deformation of amorphous alloys at room, low and elevated (below the glass transition) temperatures. The shear bands in the amorphous Al-Ni-Y are places of nanocrystal formation during the rolling deformation. As Al nanocrystal formation occurs by the diffusion mechanism; their composition is different from the composition of the amorphous matrix. The nanovoids formed by the coalescence of excess free volume during prolonged aging at room temperature were observed in the shear bands by transmission electron microscopy method. The obtained apparent diffusion coefficient in the shear band at room temperature of 10(-22) m(2)s(-1) exceeds by 5-6 orders in magnitude the diffusion coefficient in the matrix. (C) 2017 Elsevier Ltd. All rights reserved.

One central material issue in spintronics is the search for high temperature (above room temperature) magnetic semiconductors. We report on the formation of a transparent magnetic semiconductor with embedded ferromagnetic metallic glass nano-granules, showing a Curie temperature of similar to 600 K. Soft X-ray magnetic circular dichroism data verify its intrinsic room-temperature ferromagnetism. Owing to the unique structure of ferromagnetic nano-granules embedded in the hostmagnetic semiconductor, additional interfacial exchange anisotropy emerges and stabilizes the ferromagnetism. The magnetotransport measurements of the amorphous nanocomposite indicate that its anomalous Hall effect is dominated by the extrinsic mechanism of the side-jump due to the spin-dependent impurity. (C) 2017 Elsevier Ltd. All rights reserved.

Ti-Fe-Sn-Nb alloys comprised of single beta-Ti phase were developed showing excellent mechanical strength and superior plasticity. The alloys exhibited increased yield strength as a function of Fe content, where the Ti80Fe14Sn3Nb3 alloy presented the highest yield stress (1.88 GPa) comparable to that of Ti-based nanocrystalline alloys. Moreover, a significant strain-hardening (520 MPa) was achieved along with the plastic deformation. The excellent mechanical strength was enhanced by the supersaturated beta-Ti and the high density of lattice defects that restrict the dislocation motion.

Ti-Ni-Cu-Zr-based crystal/glassy dual-phase alloy samples with different sizes and good mechanical properties were manufactured. The structure of these samples was examined via X-ray Diffraction, Scanning Electron Microscopy, and Transmission Electron Microscopy. The developed dual-phase structure alloys combine the high strength of glassy alloys and plasticity of crystalline alloys. Plastic deformation was enhanced by this dual-phase structure. Mechanical characterization of the alloys revealed three deformation stages, namely a martensitic transformation, dislocation slip in a crystalline phase, and shear deformation of the glassy matrix. Two types of effects involving the martensitic transformation were observed: superelastic behavior and the transformation induced plasticity (TRIP) effect, which provide an additional deformation mechanism and lead to a significant increase in the plasticity of these dual-phase samples. The results indicate that the fraction of glassy phase occurring in large rods formed at lower cooling rates is lower than that occurring in smaller rods; therefore, the deformation-induced martensitic transformation of the crystalline cP2 phase in the large samples occurs at lower stresses.

In this letter new Ti-Fe-Sn-Nb hypoeutectic alloy comprised of primary dendritic beta-Ti and ultrafine (beta-Ti + TiFe) eutectic was developed showing superior mechanical properties. The as-cast Ti67Fe27Sn3Nb3 (at.%) alloy exhibited exceptionally high yield stress (2.18 GPa) comparable to that of bulk metallic glasses. Most importantly, the sample presented significant strain-hardening (320 MPa) and enhanced plasticity. The slip deformation and dislocation accumulation in the beta-Ti dendrite contribute to the plasticity and the pronounced strain-hardening, whereas the high strength stems from the ultrafine (beta-Ti + TiFe) eutectic structure as well as the solution hardening in the multicomponent system. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The most common hydrogen storage alloys (TiFe, Mg2Ni and LaNi5) were chosen for studying the effect of high energy ball milling (HEBM) on the ability of intermetallic powders to form bulk compact samples (pellets) by solid-state bonding without binder. The role of internal energy accumulated in the material during activation treatment on formation of contact surfaces between the particles was considered. It was shown that the consolidation of the intermetallic hydrogen storage alloys prepared by HEBM allows obtaining porous bulk nanostructured samples which demonstrate simplified hydrogen activation procedure, higher thermal diffusivity and good durability after multiple absorption-desorption cycles. (C) 2016 Elsevier B.V. All rights reserved.

Nanogranular metallic glasses (NGMGs) or metallic nanoglasses are assembly of metallic glass (MG) granules with a size typically ranging from a few to 100 nm interconnected by glass/glass interfaces. These materials can be synthesized by different techniques including inert gas condensation and physical vapor deposition. In comparison with conventional MGs produced by cooling of liquids, NGMGs show enhanced thermal stability, ferromagnetism with higher Curie temperature, better biocompatiblity and superior mechanical properties. This review aims to introduce such a new class of non-crystalline solids: NGMGs, emphasizing on the preparation methods and the unique properties of these materials. Meanwhile, an outlook on this subject is proposed for the possible future research topics in the field of nanoglasses. (C) 2016 Elsevier B.V. All rights reserved.

Accurate values needed for the most commonly used indicators of good Glass Forming Ability (GFA) in alloys, i.e. the liquidus (T-l), crystallization (T-x) and glass transition (T-g) temperatures, are only available after successful production of the metallic glass of interest. This has traditionally made discovery of new metallic glasses an expensive and tedious procedure, based on trial-and-error methodology. The present study aims at testing the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) approach for predicting GFA in the Fe-Nb-B system by the use of the Thermo-Calc software and the thermodynamic database TCFE7. The melting temperatures and phase stabilities were calculated and combined with data for an atomic size mismatch factor, lambda, in order to identify and map potential high-GFA regions. Selected compositions in the identified regions were later produced by suction casting and melt spinning, and the potential success verified using X-Ray Diffraction (XRD). Differential Scanning Calorimetry (DSC) was also used to compare thermodynamic calculations for the model predictions, and evaluate standard GFA indicators. The model is found to fit well with literature data, as well as predict new bulk glassy compositions at and around Fe70.5Nb7B22.5. These results show promise in further predictive use of the model. (C) 2016 Elsevier B.V. All rights reserved.

The electrochemical behavior and biocompatibility of the micro/nano-structured alpha+beta Ti-3.5Fe-3.9Cu alloy were investigated in this work. The alloy was produced by tilt-casting method and subjected to subsequent hot dual-axial forging at 1173 K. It is shown that the electrochemical behavior and biocompatibility of the Ti-3.5Fe-3.9Cu alloy are close to, or even better, than those of a typical commercial Ti-6Al-4V alloy widely used as implants. This demonstrates that the Ti-3.5Fe-3.9Cu alloy shows a good potential for application as biomaterial. (C) 2016 Elsevier B.V. All rights reserved.

Ti-based alloys containing Fe, Au, and Nb were produced by a tilt-casting method, subjected to a subsequent dual-axially forging operation, with their properties being studied. The research evidenced that though Ti94Fe3Au3 and Ti94Fe3Nb3 alloys had relatively high biocompatibility, they were very brittle during tensile tests. The dual-axially forged Ti94Au3Nb3 alloy exhibited relatively good tensile mechanical properties (tensile strength up to 740 MPa, elongation of similar to 13% and elastic module of similar to 85 MPa). The average value of the hemolysis of the Ti94Au3Nb3 alloy was found to be around 0.01896%. The Ti94Au3Nb3 alloy showed a good potential to be applied as a biomaterial. (C) 2016 Elsevier B.V. All rights reserved.

Bulk composites based on Cu54Pd28P18 metallic glass and polytetrafluoroethylene (PTFE of about 1 mass %) were produced by mechanical alloying method with subsequent spark plasma sintering. The spark plasma sintering was done at the temperature close to the super cooled liquid region of the metallic glass. Structure and thermal properties of the obtained metallic glass/polymeric composite samples were investigated. It was found that composite sample (Cu54Pd28P18/PTFE) has a relatively high thermal conductivity but the appearance of the crystalline phases including oxide phase (Cu2O) on the border between the metallic glass particles, affected the physical properties badly.The obtained results can be beneficial in terms of obtaining different antifriction composite materials based on metallic glass and self-lubricated polymers. (C) 2016 Elsevier B.V. All rights reserved.

The early stage of crystallization in amorphous phases is a key step in the overall microstructural evolution. In a Zr-based amorphous alloy the formation of metastable nanophase was observed at the earliest crystallization stage, with an ultra-high nucleation density of 6.5 x 10(24) m(-3) and a size of 1 2 nm. The nanophase has an icosahedral structure and exhibits an extremely high thermal stability up to 150 K above the crystallization onset. The chemical and structural heterogeneity in the early stage of the glass crystallization were observed using high-resolution high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), which can be applied to study materials with atomic resolution. A nucleation kinetics analysis of the nanophase formation accounts for the high product number density and indicates a low interface energy value between the metastable clusters and the amorphous matrix, sigma(a,i) of 14 mJ/m(2). The thermal stability and resistance to size change by growth or coarsening are attributed to a stalled growth due to solute depletion and the low cw value. With the high nucleation rate and the low barrier, it is remarkable that the kinetics follow conventional nucleation theory. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Uniaxial compression is used to apply cyclic loading within the elastic range to samples of Zr61Cu27-Fe2Al10 bulk metallic glass (BMG). The results are twofold. On one hand the microhardness measured on the end-faces of the samples shows an increase of similar to 8% together with a slight gradual increase in the Young's modulus after the 2nd cycle. This appears similar to hardening induced by elastic cycling in nanoindentation. The microhardness measured in the centre of the sample or on the side faces of the BMG samples show little or no change as a result of cyclic loading. These results suggest that the apparent hardening of the end-faces is a surface effect attributed, not to relaxation, but to a build-up of anelastic strain, associated with local anisotropy and stresses arising from uneven loading of the samples. This is confirmed by the decay of the apparent hardening after a several days of natural ageing at room temperature. On the other hand an effect similar to structure rejuvenation takes place in the central part of the samples leading to higher specific heat capacity of the cycled samples, larger crystallization and relaxation enthalpies. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

This paper describes investigation of the mechanical properties and biocompatibility of the Ti-based low-alloys minor alloying by the noble metal. It was found that almost all of the investigated Ti-based low-alloys, minor alloying by the noble metal, have relatively high biocompatibility, but found to be very brittle during tensile tests. The Ti94Au3Nb3 alloy exhibited relatively good tensile mechanical properties, having very good plasticity.

A relatively small number of revolutionary materials have been discovered in the field of physical metallurgy and metal physics in the last several decades, and bulk metallic glasses are among them. Their strength and hardness are considerably higher and their modulus of normal elasticity is considerably lower than that of crystalline alloys, which leads to large stored elastic strain energy. These materials also have very good corrosion resistance. In this article, we present the properties of bulk metallic glasses, in particular, thermal, mechanical, magnetic, and electrical properties, corrosion resistance, as well as the application fields of these alloys.

Morphology evolution of the multicomponent metallic glass film obtained by radio frequency (RF) magnetron sputtering was investigated in the present work. Two modes of metallic glass sputtering were distinguished: smooth film mode and clustered film mode. The sputtering parameters, which have the most influence on the sputtering modes, were determined. As a result, amorphous Ni-Nb thin films with a smooth surface and nanoglassy structure were deposited on silica float glass and Si substrates. The phase composition of the target appeared to have a significant influence on the chemical composition of the deposited amorphous thin film. The differences in charge transport and nanomechanical properties between the smooth and nanoglassy Ni-Nb film were also determined.

We demonstrate, for the first time, that the (Fe0.75B0.15Si0.1)(100-x)Nb-x (x = 0,1 and 3 at metallic glasses without toxic and allergic elements exhibit excellent apatite-forming ability in simulated body fluids (SBF), which is expected to be a new generation of biomaterials in stents and orthopedic implants. For the alloys without any surface treatment, spherical particles corresponding to octacalcium phosphate are spontaneously nucleated and precipitated throughout the alloy surface after immersion only for 1 clay, indicating that the present alloys possess an unusual high bioactivity. During the subsequent in-vitro immersion for 3 days, SEM image reveals the typical 'cauliflower' morphology of bone-like hydroxyapatite (HA) with Ca/P ratio of 1.65. In addition, it is surprising to find that the in-vitro SBF immersion not only leads to the formation and growth of the apatite layer but also causes the progressive development of the underlying alloy substrate. Moreover, for the alloys immersed for 3 or 9 days, the substrate alloy just beneath the apatite layer consists of a hierarchical nano/macroporous structure through selective dissolution of the active components Fe and B in the surface. XPS analysis indicates that the apatite nucleation on the present alloys in SBF is attributed to the specific dissolution properties of the present alloys and the fast formation of Si-OH and Fe-OH or Nb-OH functional groups, followed by combination of these groups with Ca2+ and phosphate ions. (C) 2016 Elsevier B.V. All rights reserved.

Metallic glasses are found to be applicable in micromechanical systems. When the size of the mechanical components is reduced to the micrometer and sub-micrometer level, the native surface oxide layer starts playing an important role in contact mechanical applications of metallic glasses. The nanoscale and atomic-scale scratch wear resistance of metallic glasses is studied in the present work using an atomic force microscopy at different loads. The wear rate is correlated with the properties of the metallic glasses studied and their respective surface oxides. (C) 2016 Elsevier B.V. All rights reserved.

Emerging for future spintronic/electronic applications, magnetic semiconductors have stimulated intense interest due to their promises for new functionalities and device concepts. So far, the so-called diluted magnetic semiconductors attract many attentions, yet it remains challenging to increase their Curie temperatures above room temperature, particularly those based on III-V semiconductors. In contrast to the concept of doping magnetic elements into conventional semiconductors to make diluted magnetic semiconductors, here we propose to oxidize originally ferromagnetic metals/alloys to form new species of magnetic semiconductors. We introduce oxygen into a ferromagnetic metallic glass to form a Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor with a Curie temperature above 600 K. The demonstration of p-n heterojunctions and electric field control of the room-temperature ferromagnetism in this material reflects its p-type semiconducting character, with a mobility of 0.1 cm(2) V-1 s(-1). Our findings may pave a new way to realize high Curie temperature magnetic semiconductors with unusual multifunctionalities.

A method of composition design for metallic glasses was proposed by using the Calculation of Phase Diagrams (CALPHAD) with the assistance of the topological instability criterion. This methodology was demonstrated in the quick and effective searching of glass-forming regions for Ti-Fe-Si and Ti-Zr-Fe-Si alloys containing no biologically toxic elements, e.g., Ni and Cu. In addition, the Ti-Fe-Si system may promote the glass formation owing to the existence of a deep eutectic at the Ti-rich corner. A self-consistent thermodynamic database was constructed based on the CALPHAD approach. The liquidus projection, isothermal sections, and the enthalpy of mixing were calculated by using the database. On the basis of these calculations coupling with the topological instability "lambda lambda criterion," the potential glass-forming alloy compositions in a narrow region were suggested for experimental validation. Thereafter, the isothermal sections of the Ti-Zr-Fe-Si quaternary system were calculated at certain contents of Zr. The designed alloys were prepared by arc-melting and followed by melt-spinning to the ribbon shape. The experimental verifications matched reasonably well with the theoretical calculations. This work offers new insights for predicting glass-forming alloys based on thermodynamic arguments; it shall be of benefit for the exploration of new metallic glasses. Published by AIP Publishing.

The plot scaling of viscosity by the reduced temperature as an important and vivid representation of the liquid fragility property has been utilized by materials scientists for more than four decades. In the present manuscript we discuss practical limitations on the high temperature part of the viscosity plot. It is valid up to the boiling point at pressure ranges from the triple point to the critical pressure and nearly up to the critical temperature at high pressure. Although, the high temperature viscosity estimation at T -&gt; infinity is rather a result of overestimation of an Arrhenius or VFTH equitation fitting and does not have a physical meaning more attention is required to shed light on the behavior of glass-forming liquids in this temperature range by taking into account the supercritical liquid phenomenon. (C) 2016 Elsevier B.V. All rights reserved.

The La55Al25Cu10Ni10-10 vol.% Ti glassy composites have excellent compressive strength and plasticity at room temperature (RT). At cryogenic temperature (77 K), neither the glassy matrix, nor the Ti particles undergo embrittlement, and the composite retains appreciable toughness. Surprisingly, despite significant shear band plasticity at 77 K, failure occurs in a mixed mode manner, with large areas showing quasi-cleavage features that appear to initiate from cracks at the glass-Ti interfaces, which also limit the overall plastic strain. Interface engineering is the key to further alloy development for even better properties. (C) 2016 Elsevier Ltd. All rights reserved.

Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/ crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

Composition modification of (Ti-Ni)-(Cu-Zr) alloys with addition of Y, Co, Nb, Al and B was performed with the purpose of production of high-strength crystal-glassy phase composites. The structure of these samples with an amorphous phase was examined by X-ray diffraction, scanning and transmission electron microscopy. It was found that the addition of Y does not lead to increase in the glass forming ability of the Ni-Ti-Cu-Zr system alloys. Dual-phase structure allows developing the composite materials, which combine high strength of glassy alloys and good plasticity of crystalline alloys. Sixteen different alloy compositions were prepared and investigated. Mechanical characteristics of the alloys were determined using universal testing machines. For example, Ti40Ni39.5Cu8Zr10Co2Y0.5 alloy showed the compressive strength about 2600 MPa and total strain about 25%. Transformation-induced plasticity and superelasticity effects were found to exist. Large amount of Y (more than 0.5 at%) induces precipitation of the NiTi2 phase which is harmful for mechanical properties. The addition of Nb, Al and B leads to increase in yield strength, but Al and B suspend martensitic transformation and as a result these alloys have lower overall plasticity. The specimens demonstrate a good combination of strength and plasticity owing to both the composite effect of a dual-phase structure and the dynamic martensitic transformation that develops during deformation. (C) 2015 Elsevier B.V. All rights reserved.

In our research we obtained composites based on high-density polyethylene (HDPE) reinforced with Mg67,5Ca5Zn27,5 metallic glass by co-extrusion and compression. The co-extrusion and compression procedures have been provided at temperatures of supercooled liquid temperature region of both materials (between the glass transition temperatures (T-g) and crystallization temperature (T-x)). We investigated the mechanical properties and performed the structure characterization of the obtained polymeric/metallic glass composite samples. A positive effect of triethoxyvinylsilane on the adhesion between polymeric matrix and metallic glass reinforced particles was discovered. It was also found that composite samples (HDPE/Mg67,5Ca5Zn27,5) had excellent adhesion, good thermal conductivity and high modules of elasticity. The metallic glassy samples demonstrated good dimensional stability after treatment by the 10 mass% of the triethoxyvinylsilane. (C) 2015 Elsevier Ltd. All rights reserved.

The present work is devoted to an investigation of the microstructure, deformation behavior and kinetics of crystallization of Zr-based glassy alloys produced in a low vacuum environment. The data obtained indicate that small additions of rare earth (RE) metals, such as Dy, Gd, Er, to a Zr62.5Cu22.5Fe5Al10 alloy are likely to suppress heterogeneous nucleation of impurities, and thus, increase the glass forming ability (GFA), which allows obtaining glassy ingots up to 5 mm diameter even under a low vacuum. The structure of the alloys consisted of a glassy matrix and a small fraction of RE oxides. The large difference between the enthalpies of the oxide formation of copper and RE elements is responsible for the reduction of copper concentration in the regions near the oxides. According to the kinetics parameters of crystallization, the highest thermal stability observed in a Gd-bearing alloy corresponds to its good GFA. The maximum compression strength was achieved in the alloy containing 0.5 at.% of Dy. At the same time, the optimal combination of strength and plasticity, with the fracture strength of 1890 MPa and the plastic deformation of 3.3%, was observed in the alloy containing 1 at.% of Gd. A finite element modeling (FEM) analysis showed that equiaxed oxide particles can prevent propagation of a single shear band and promote generation of multiple shear bands. (C) 2015 Elsevier B.V. All rights reserved.

Bulk metallic glasses (BMGs) of Pd-Cu-Si and Pd-Ni-P systems were formed from a melt in the 1970s-1980s. However, in view of the extremely high cost of the main component (palladium), they have been outside the realm of special interest of scientists and engineers for a long time. Relatively recently, BMGs in the form of macroscopic-sized ingots have been fabricated in alloys based on industrial metals (iron, copper, magnesium, and titanium), which opened up wide possibilities for their application. BMGs possess high strength, hardness, wear resistance, elastic deformation, and corrosion resistance. In this study, a review of publications is presented and main scientific achievements in this field are described. It is noted that main scientific problems, which are not solved completely, are describing the BMG structure as well as vitrification and plastic deformation, while the technical problem attracting the attention of scientists in many countries is to increase the plasticity and impact fracture toughness of these materials.

Methods to strengthen aluminum alloys have been employed since the discovery of the age-hardening phenomenon in 1901. The upper strength limit of bulk Al alloys is similar to 0.7 GPa by conventional precipitation strengthening and increases to 41 GPa through grain refinement and amorphization. Here we report a bulk hybrid nanostructured Al alloy with high strength at both room temperature and elevated temperatures. In addition, based on high-resolution transmission electron microscopic observations and theoretical analysis, we attribute the strengthening mechanism to the composite effect of the high-strength nanocrystalline fcc-Al and nano-sized intermetallics as well as to the confinement effect between these nano phases. We also report the plastic deformation of nano-sized intermetallics and the occurrence of a high density of stacking faults and twins in fcc-Al after low-strain-rate deformation at room and high temperatures. Our findings may be beneficial for designing high-strength materials for advanced structural applications.

In this work, we investigated the microstructure and mechanical properties of Al25Ti25Ni25Cu25Al22.5Ti22.5Ni20Cu20Fe15 and Al20Ti20Ni20Cu20Fe20 high entropy alloys, produced by arc melting and casting in an inert atmosphere. The structure of these alloys was studied by X-ray diffractometry and scanning electron microscopy. The as-cast alloys were heat treated at 773, 973 and 1173 K for 1800 s to investigate the effects of aging on the plasticity, hardness and elastic properties. Compared to the conventional high-entropy alloys the Al25Ti25Ni25Cu25, Al22.5Ti22.5Ni20Cu20Fe15 and Al20Ti20Ni20Cu20Fe20 alloys are relatively hard and ductile. Being heat treated at 973 K the Al22.5Ti22.5Ni20Cu20Fe15 alloy shows considerably high strength and relatively homogeneous deformation under compression. The plasticity, hardness and elastic properties of the studied alloys depend on the fraction and intrinsic properties of the constituent phases. Significant hardening effect by the annealing is found. (C) 2015 Elsevier B.V. All rights reserved.

A melt-spun Fe90Si5B5 alloy ribbon consists of bcc-Fe(Si) + Fe3B + amorphous phase and exhibits good bending ductility, high tensile fracture strength above 1000 MPa, high corrosion resistance and unique magnetic properties as exemplified for high saturation magnetization exceeding 1.9 T, moderately high initial permeability of about 150 and low coercivity of 745 A/m which are attractive for magnetic sensors utilizing a nearly constant high permeability with applied field up to coercivity. Besides, the tensile fracture strength and elongation increase significantly to 1286 MPa and 0.62%, respectively, after annealing for 900 s at 823 K. The Fe-Si-B alloy ribbons are attractive as a new type of sensor material with features of high bending ductility, high tensile strength and elongation, relatively good corrosion resistanceand unique soft magnetic properties with very high saturation magnetization.

Formation of a native oxide layer on the surface of bulk metallic glasses (BMGs) influences significantly the nanoscale tribological properties and mechanical behavior of the BMGs used in nanodevices. However, our knowledge of the native oxidation process on the BMG surface and structure of the corresponding oxides remains limited because the oxide layer is very thin. Here we conducted a combined state-of-the-art experimental technique study of the atomic structure, oxidations states and electrical conductivity of the native surface oxides on a Cu-Zr-Al BMG formed at ambient conditions by aberration-corrected scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS) and conductive atomic force microscopy (AFM). This allowed shedding light on the atomic structure, metal oxidation state, growth behavior and nanoscale electrical properties of the surface oxide. The conductive AFM measurements reveal that the electrical conductivity of the native oxide layer transits from the initially metallic to a nonlinear one after some air exposure, and finally changes to insulative state. These findings represent a significant step forward in the knowledge of surface oxides and open up the possibility of fabricating nanoscale electrical devices based on BMGs with controllable conductivity. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

When a spatially uniform temperature change is imposed on a solid with more than one phase, or on a polycrystal of a single, non-cubic phase (showing anisotropic expansion-contraction), the resulting thermal strain is inhomogeneous (non-affine). Thermal cycling induces internal stresses, leading to structural and property changes that are usually deleterious. Glasses are the solids that form on cooling a liquid if crystallization is avoided-they might be considered the ultimate, uniform solids, without the microstructural features and defects associated with polycrystals. Here we explore the effects of cryogenic thermal cycling on glasses, specifically metallic glasses. We show that, contrary to the null effect expected from uniformity, thermal cycling induces rejuvenation, reaching less relaxed states of higher energy. We interpret these findings in the context that the dynamics in liquids become heterogeneous on cooling towards the glass transition(1), and that there may be consequent heterogeneities in the resulting glasses. For example, the vibrational dynamics of glassy silica at long wavelengths are those of an elastic continuum, but at wavelengths less than approximately three nanometres the vibrational dynamics are similar to those of a polycrystal with anisotropic grains(2). Thermal cycling of metallic glasses is easily applied, and gives improvements in compressive plasticity. The fact that such effects can be achieved is attributed to intrinsic non-uniformity of the glass structure, giving a non-uniform coefficient of thermal expansion. While metallic glasses may be particularly suitable for thermal cycling, the non-affine nature of strains in glasses in general deserves further study, whether they are induced by applied stresses or by temperature change.

In the present paper, the glass-transition phenomenon in an Au-based metallic glass has been studied using a step-scan calorimetiy measurement. The existence of two distinct slopes within the glass-transition region one starting at low temperature (about 340 K) and the other at higher temperature (about 380 K) likely indicates two glass-transition processes. This phenomenon is rather related to different diffusion coefficients of the alloying elements in this complex alloy in solid state. Structural relaxation of the glassy phase before reaching the glass-transition region also shows a complex behavior. (C) 2015 Elsevier B.V. All rights reserved.

We examined the formation, thermal stability, mechanical properties and corrosion behavior of a multicomponent Zr55Al10Fe6Co6Ni6Cu6Pd6Ag5 bulk glassy alloy, with the aim of clarifying the effect of high-order multiplication of the number of components on their properties. The bulk glassy alloy rods of 2 and 6 mm in diameter were formed by suction casting even at the low total content of typical glass-forming 3-d late transition metals like Co, Ni and Cu. The Vickers hardness is different in the center region and in the outer surface region. The difference seems to reflect the relaxation level of glassy structure. The Young's modulus and the compressive fracture strength are nearly the same for the base Zr55Al10Ni5Cu30 alloy in spite of the existence of immiscible atomic pairs. Moreover, the multicomponent alloy exhibits better corrosion resistance than that for the base alloy. The glassy phase changes to a supercooled liquid state at 720 K and then starts to crystallize at 754 K with a single exothermic peak, in contrast to the appearance of a wide supercooled liquid region for the base alloy. The primary crystalline phase precipitates with very short incubation time and very low growth rate, which are different from those for the base alloy. The extremely low growth rate of the crystallites is presumably due to the reduction of diffusivity of late transition metal elements resulting from multiplication. Thus, the high-order multiplication has the features of (1) the maintenance of high glass-forming ability even at the lower Co, Ni and Cu content and in the absence of wide supercooled liquid region, (2) the suppression of the decrease in mechanical strength even in the dissolution of immiscible elements, (3) better corrosion resistance, and (4) low growth rate of the primary precipitates. (C) 2015 Elsevier B.V. All rights reserved.

In the present work we study and compare the crystallization behavior of Fe- and Co-based good bulk glass formers with an exceptionally high glass-forming ability leading to the critical thickness of cast samples reaching 1 cm. For Fe-based alloys we also investigate the effect of opposite C/B content ratio on the glass-forming ability and the crystallization behavior. The structure and phase composition of the glassy samples were examined by conventional X-ray diffractometry and transmission electron microscopy while thermal stability and phase transformations were studied by differential scanning calorimetry. The reasons for high glass-forming ability are discussed. The glass-forming ability of the studied alloys depends on both factors: the type of crystallization reaction and characteristic temperatures. (C) 2015 Elsevier B.V. All rights reserved.

The thermoelectric properties of Au49Cu26.9Ag5.5Pd2.3Si16.3 glassy alloy have been studied using electrical resistivity, thermal conductivity and Seebeck coefficient measurements over temperature range 2-390 K. At heating, resistivity rho decreases in a power-law manner from residual value rho(0) similar to 150 mu I (c) cm. The temperature coefficient of resistivity, alpha = rho(-1)(a,rho/a,T), is rather small and varies non-monotonously. Thermal conductivity kappa rises linearly at low temperatures; it exhibits a plateau-like feature and sharply increases at elevated temperatures. Seebeck coefficient S increases with temperature and exhibits a characteristic "knee" feature. At elevated temperatures, S increases linearly with temperature but with a different slope. It total, thermoelectric properties of Au-based glassy alloy demonstrate behavior of a highly disordered system in a most pronounced manner.

A common understanding of plastic deformation of metallic glasses (MGs) at room temperature is that such deformation occurs via the formation of runaway shear bands that usually lead to catastrophic failure of MGs. Here we demonstrate that inhomogeneous plastic flow at nanoscale can evolve in a well-controlled manner without further developing of shear bands. It is suggested that the sample undergoes an elasto-plastic transition in terms of quasi steady-state localized shearing. During this transition, embryonic shear localization (ESL) propagates with a very slow velocity of order of similar to 1 nm/s without the formation of a hot matured shear band. This finding further advances our understanding of the microscopic deformation process associated with the elasto-plastic transition and may shed light on the theoretical development of shear deformation in MGs.

Here, we report on the properties of native and artificial oxide amorphous thin film on a surface of an amorphous Ni-Nb sample. Careful measurements of local current-voltage characteristics of the system Ni-Nb / NiNb oxide/Pt, were carried out in contact mode of an atomic force microscope. Native oxide showed n-type conductivity, while in the artificial one exhibited p-type one. The shape of current-voltage characteristic curves is unique in both cases and no analogical behavior is found in the literature. X-ray photoelectron spectroscopy (XPS) measurements were used to detect chemical composition of the oxide films and the oxidation state of the alloy components. Detailed analysis of the XPS data revealed that the structure of natural Ni-Nb oxide film consists of Ni-NbOx top layer and nickel enriched bottom layer which provides n-type conductivity. In contrast, in the artificial oxide film Nb is oxidized completely to Nb2O5, Ni atoms migrate into bulk Ni-Nb matrix. Electron depletion layer is formed at the Ni-Nb/Nb2O5 interface providing p-type conductivity. (C) 2015 AIP Publishing LLC.

In the present work, we discuss the glass-forming ability of various binary alloys in which the glassy phase was not formed even by melt spinning technique with high cooling rate of the melt up to 1 MK/s (some consisted of partly glassy phase), though by commonly accepted guidelines, these alloys could be as good glass-formers as many other binary glasses. The alloys studied belong to binary systems with multiple eutectics; the constituent elements have a negative enthalpy of mixing, and a significant variability of atomic size differences is observed from system to system. The results indicate the necessity of taking into account simultaneously various factors influencing the glass-forming ability including melt fragility.

In the present work we study the formation mechanism and crystallization behavior of Fe-based bulk metallic glasses influenced by the addition of rare-earth elements. Samples are characterized by conventional X-ray diffractometry, optical microscopy, and high-resolution fielde-mission-gun scanning and transmission electron microscopy. In the rare-earth-containing alloys, bulk metallic glasses are formed with populations of quenched-in nuclei. Consequently, crystallization on isothermal annealing occurs without any incubation period. This behavior, not typical of bulk metallic glasses in general, implies that in the rare-earth-containing alloys glass formation is possible only because of restricted crystal growth: both on cooling from the molten and on heating from the glassy state, growth of the primary chi-Fe36Cr12Mo10 crystals is too slow to be significant on a reasonable timescale. The low growth rate is connected with large inhomogeneous strain in the growing nanoparticles, while nucleation of eutectic colonies is hampered by slow diffusion of a rare-earth alloying element. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Zr-Pd metallic glassy thin films with a hierarchical nano-scale structure, produced by magnetron sputtering of the Zr and Pd powder mixture, demonstrate a unique combination of physical and biochemical properties. Thermal stability of the nano-structured glassy samples, their resistance to oxidation in dry air and phase transformation behavior are discussed in the present work. These binary alloy samples also show exceptionally high corrosion resistance and spontaneous passivation in a simulated body fluid. Experiments on the catalytic activity and biocompatibility of this nanostructured metallic glass indicate that this is a very suitable material for biochemical applications. Compared to the multicomponent alloys studied earlier this binary alloy has much simpler chemical composition, which makes preparation of the sample with defined stoichiometry easier, especially when the elements have different sputtering rates.

Synthesized from ultrafine particles with a bottom-up approach, nanoglasses are of particular importance in pursuing unique properties. Here, we design a metallic nanoglass alloy from two components of similar to Cu64Sc36 and similar to Fe90Sc10 nanoglasses. With nanoalloying mutually immiscible Fe and Cu, the properties of the nanoglass alloys can be tuned by varying the proportions of the similar to Fe90Sc10 component. This offers opportunity to create novel metallic glass nanocomposites and sheds light on building a structure-property correlation for the nanoglass alloys.

We have developed a torsion machine that can apply pure shear stress to small-diameter rod samples. We report preliminary results on Cu-based metallic glass samples held at constant torque in the elastic range. The inelastic angle of twist increases approximately linearly with the logarithm of time, interpreted as anelastic deformation. Reversal of torque reveals an effect analogous to the Bauschinger effect in polycrystalline metals. The relative deformation rate is increased by a factor of 4.5 on first reversal, an effect discussed in terms of the operation of shear transformation zones and related to structural change in the metallic glass. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.

We investigated the microstructure and mechanical properties of Ti20Zr20Hf20Nb20X20 (X = V or Cr) high-entropy alloys (HEA), produced by induction melting and casting in inert atmosphere. The structures of these alloys were studied via X-ray diffractometry and scanning electron microscopy. Results show that Ti20Zr20Hf20Nb20X20 has mainly the body centered cubic (BCC) structure, whereas the BCC matrix of Ti20Zr20Hf20Nb20X20 contains small amount of Cr2Nb and Cr2Hf intermetallic compounds. Ti20Zr20Hf20Nb20X20 alloy shows the high strength and the homogeneous deformation under compression at room temperature. The strength and hardness of Ti20Zr20Hf20Nb20X20 alloy are further enhanced by the Cr-containing Laves phases segregated during casting. The structural and mechanical properties remained almost unchanged after a short time (10 min) heat treatment at 573, 773, 973 and 1173 K indicating the resistance to working temperature peaks for these two alloys. Ab initio calculations predict ductile behavior for these and similar refractory HEM. The theoretically calculated Young's modulus E is in good agreement with the experimental ones. (C) 2014 Elsevier Ltd. All rights reserved.

Fe-rich amorphous alloys with minor-addition of Cr and/or Nb were examined with the aim of developing Fe-based amorphous alloys exhibiting simultaneously high saturation magnetization above 1.5 T and good corrosion properties. Fe82Cr2B8P4Si3C and Fe82NbB9P4Si3C amorphous alloys were found to exhibit high saturation magnetizations of 1.49 T and 1.57 T, respectively, and rather good corrosion resistance in 3.5 mass% NaCI solution at 298 K. The minor-addition of Cr or Nb enables the formation of amorphous alloy particles without harmful oxide layer by water atomization process which makes these alloys suitable for applications as soft magnetic core materials. The addition of 1 at% Nb improved the corrosion resistance through the increase in E-corr value, which makes easy to reach passive state, and the suppression of pitting corrosion. Besides, it has been proved that the simultaneous addition of Nb and Cr has an effect on forming protective passive film. (C) 2014 Elsevier Ltd. All rights reserved.

Samples of Zr62.5Cu22.5Fe5Al10 bulk metallic glass are subjected to uniaxial compression. Comparison of tests in monotonic loading and cyclic loading (repeated loading to the onset of plasticity, then unloading) shows that the compressive plasticity of the glass is drastically reduced under cyclic loading. It is argued that this effect arises from stress reversal accelerating the concentration of shear on a dominant shear band. The link with compression-compression fatigue results, and the consequences for low-cycle fatigue of metallic glasses are considered.

Ultrastable glasses and nanoglasses are two emerging materials with novel properties that have been investigated separately. In order to explore the combined effect of ultrastable character and a nanoglass with a nanoglobular microstructure on the kinetic behavior, the glass transition and crystallization behaviors of an ultrastable nanoglass and a melt-spun ribbon of Au-based metallic glass were examined by differential scanning calorimetry at heating rates (phi) of up to 40,000 K s(-1). The nanoglass shows ultrastable kinetic characters at low phi (e.g. 300 K s(-1)) and similar kinetic behaviors at high phi (e.g. 30,000 K s(-1)) compared to the melt-spun ribbon. The nanoglobular interfaces remain amorphous and appear to act as a kinetic constraint to induce a higher crystallization temperature compared to the melt-spun ribbon. The interface constraint effect disappears at 30,000 K s(-1). These results indicate that the nanoglobular microstructure can act to increase metallic glass stability and provide another mechanism for the synthesis of ultrastable glass. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

In the present work Zr-based bulk metallic glassy samples with low aspect ratio (1:2) were deformed plastically at quasistatic loading conditions in order to study propagation of relatively homogeneous plastic deformation without clear shear localization in a dominant shear band that was observed in the samples with larger aspect ratio. Usage of low aspect ratio allows achieving large plastic deformations without fracture by forming multiple shear bands. The experimental results are discussed and compared with those of molecular dynamics and finite elements model computer simulation. (C) 2014 Elsevier B.V. All rights reserved.

In the present work we introduce a micro/nano-structured alpha+beta Ti-based low-alloy produced by the tilt-casting method and subjected to subsequent thermo-mechanical treatment. After hot dual-axial forging at 900 degrees C, subsequent heating at 700 degrees C and water quenching a Ti94Fe3Cu3+1000 ppm of boron alloy, containing inexpensive alloying elements, showed an ultimate tensile strength value of about 950 MPa and percentage elongation of about 5.2%. It is shown that the intensive forging treatment and subsequent heat treatment are leading to significantly improved mechanical properties of such an alloy compared to the as-cast state. (C) 2014 Elsevier B.V. All rights reserved.

The deformation behavior of bulk metallic glasses and dual-phase crystal/glassy materials was analyzed using the stress-strain diagrams, in-situ video recording and subsequent macro- and micro-structure observation. As a result a two-stage deformation mechanism is observed. The stages are related to the initiation and propagation of multiple shear bands in the beginning of the deformation process as well as the formation and propagation of the dominant shear band at the later stage finally leading to large shear offsets and failure of the sample. (C) 2014 Elsevier B.V. All rights reserved.

The microstructure of light element containing Al25Ti25Ga25Be25 equi-molar composition alloy was investigated by X-ray diffractometry and scanning electron microscopy, while the corrosion behavior was tested in 1M sulfuric acid solution (H2SO4) at ambient temperature (298 K). The results show that the alloy displays good general corrosion resistance. The influence of the microstructure and morphology of the constituent phases is also evaluated.

The crystallization kinetics and structural changes of a few metallic glassy alloys were monitored using X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. Microstructural observations were used to estimate the nucleation and growth rates. A clear comparison of the differences in the crystallization kinetics in the metallic glassy samples is observed at the early and later crystallization stages. (C) 2013 Elsevier B.V. All rights reserved.

The phenomenon of vitrification on cooling, also called the glass-transition still remains not fully understood. Recent studies by different techniques were performed in order to shed light on this and on the converse phenomenon of devitrification. Devitrification may either lead to the formation of a supercooled liquid, a crystal(s) or a quasicrystal(s). The present paper is a review of recent findings on the processes of vitrification and devitrification in metallic glasses. (C) 2012 Elsevier B.V. All rights reserved.

Nanocrystalline Mg2Ni intermetallic compound was produced from elemental components by induction melting and subsequent mechanical alloying in a planetary ball mill. Then the powder was compacted into bulk samples keeping the nanocrystalline structure. Hydrogen storage capacity of the Mg2Ni bulk samples was found to be of about 1.9 wt.%. The absorption isotherm had a long plateau, corresponding to pressure of 0.1 MPa at the temperature of 553 K. The bulk samples demonstrated high durability after 21 absorption-desorption cycles. (C) 2012 Elsevier B.V. All rights reserved.

This article is devoted to the investigation and simulation of the crystallization kinetics of zirconium-based bulk metallic glasses under heating with a constant rate, as well as under isothermal holding at an elevated temperature. The investigation into crystallization kinetics with time can provide a deeper under-standing of the crystallization mechanism of bulk metallic glasses and promote the scientifically substantiated selection of thermal treatment modes to form the desired structure and properties of composite materials on their basis.

In comparison of a Pt57.5Cu14.7Ni5.3P22.5 metallic glass with a Pt(111) single crystal we find that wearless friction is determined by chemistry through bond formation alloying, while wear is determined by structure through plasticity mechanisms. In the wearless regime, friction is affected by the chemical composition of the counter body and involves the formation of a liquid-like neck and interfacial alloying. The wear behavior of Pt-based metallic surfaces is determined by their structural properties and corresponding mechanisms for plastic deformation. In the case of Pt(111) wear occurs by dislocation-mediated homogeneous plastic deformation. In contrast the wear of Pt57.5Cu14.7Ni5.3P22.5 metallic glass occurs through localized plastic deformation in shear bands that merge together in a single shear zone above a critical load and corresponds to the shear softening of metallic glasses. These results open a new route in the control of friction and wear of metals and are relevant for the development of self-lubricated and wear-resistant mechanical devices.

A comparative analysis has been presented of structural features of palladium-based bulk metallic glasses prepared by argon gas casting into a copper mold after treatment of melts with a flux and studied using X-ray synchrotron radiation. The radial distribution functions have been calculated. The short-range order (in the first and second coordination shells) and the medium-range order (from the third to several subsequent coordination shells) in atomic arrangement have been analyzed.

Metallic glasses due to their unique combination of physical and chemical properties have a great potential in various applications: materials for construction, medical, MEMs devices and so on. The deformation mechanism in metallic glasses is very much different from that in conventional crystalline materials and not yet fully understood. Here we are trying to find out what drives shear deformation in metallic glasses. The compression experiments of the bulk metallic glassy (BMG) samples coated with tin, Rose metal and indium were performed. There were no melting sites of the coating observed near individual shear bands. Melting occurred only near fracture surface, near microcracks and in the places of shear band concentrations. The results indicate that shear banding is rather a stress driven process while the temperature rise that was observed takes place due to friction forces in the viscous supercooled liquid thin layer in the shear bands.

Magnesium-based metallic glasses (MMGs) show intriguing potentials for application as implantable biomaterials owing to their disordered atomic structure, good biodegradability, low elastic modulus, high strength, and large elasticity. However, despite of all these advantages, their brittleness is their Achilles' heel, which severely limits their application as biomedical materials. In the current study, a significantly improved ductility of MMGs under bending and tensile loading through minor alloying with rare-earth element ytterbium (Yb) at an atomic concentration of 2 and 4% is reported. The enhanced ductility is attributed to the increased density of shear bands close to fracture end and larger plastic zones on the fracture surface. In comparison with that of Yb-free control, in vitro cell culture study confirms an improved biocompatibility of MMGs alloyed with Yb as determined by MTT, live-dead, and cytoskeleton staining assays, respectively.

The structure of specimens of Ni-Cu-Ti-Zr alloys with an amorphous phase has been examined by X-ray diffraction, as well as by transmission and scanning electron microscopy. Mechanical characteristics of the alloys have been determined using universal testing machines. Transformation-induced plasticity has been found to exist. The specimens demonstrate a good combination of strength and plasticity owing to both the composite effect of a heterophase structure and the dynamic martensitic transformation that develops during deformation.

As-cast Ti-Cu-based alloys containing 1000 mass ppm of boron were investigated in the present work. With respect to a base compositional formula of (Ti-Zr)49.5+x(Cu-Ni)49.5-xFe1, we investigated the effect of sample size on the phase constitutions and related mechanical properties of the alloys, with the goal of producing crystal-glassy composites. The effect of Fe addition on the phase constitution of as-cast Ti-Cu-based alloys was also investigated, and the obtained results were compared with those of our previous studies, in which we investigated similar alloys containing no Fe. It was demonstrated that the addition of Fe leads to the formation of a CuTi2 intermetallic compound, while decreasing the cooling rate (by increasing the diameter of the as-cast billets) makes the formation of the CuTi2 intermetallic compound more favourable. The best combination of mechanical properties was obtained for the alloys containing no CuTi2 intermetallic compound. © 2013 Elsevier B.V.

The Ni50Pd30P20bulk metallic glass was produced by flux treatment and casing. The formation of a glassy structure of the studied alloy was confirmed by X-ray diffractometry and transmission electron microscopy. Its deformation behavior under uniaxial compression at room temperature was studied at the strain rate of 5 × 10-4s -1as well as at three different strain rates at the quasistatic loading conditions. The serrated flow behavior appears to be chaotic and is analyzed with a stochastic model. The model suggests that the underlying serrated slow dynamics initially results from the appearance of new shear bands in the material, but as the experiment proceeds the nature of these dynamics change, and strain takes place by the enlargement of shear bands already present on the material. © 2013 Elsevier B.V. All rights reserved.

ISSN 1882-9465

Metallic glasses demonstrate unique properties, including large elastic limit and high strength, which make them attractive for practical applications. Unlike crystalline alloys, metallic glasses, in general, do not exhibit a strain hardening effect, while plastic deformation at room temperature is localized in narrow shear bands. Room-temperature mechanical properties and deformation behavior of bulk metallic glassy samples and the crystal-glassy composites are reviewed in the present paper.

La55Al25Cu10Ni10 metallic glass has been reinforced with 325-mesh Ta particles to obtain ex situ glass-crystal composites. The composites show a high compressive plasticity (40%) with a minor reduction (similar to 8%) in yield strength-a combination unprecedented for La-based systems and even surpassing some Zr-based glassy composites that utilize a tougher matrix. However, it is also found that the plastic strain is apparently sensitive to defects, like oxides, in the glassy matrix.

We report on the formation of a transparent magnetic material containing nanocrystalline face-centered cubic (FCC) Ni produced by selective oxidation of Ni62Nb38 glassy alloy. Our results demonstrate the formation mechanism and provide the detailed structural characterization of the samples obtained. The proposed oxidation de-alloying method provides a simple way of producing samples containing fine nanocrystalline FCC Ni (average size similar to 3 nm) particles homogeneously distributed in an amorphous Nb2O5 matrix which is applicable as a magneto-optic material. (C) 2013 Elsevier B.V. All rights reserved.

This work presents a comparative study of different properties variation of Pd40Ni40Si5P15 bulk metallic glass (BMG), namely: density, hardness, relaxation enthalpy and mechanical properties as a function of the sample thickness. The samples were produced in the form of a long pyramid by conventional Cu-mold casting in an Ar atmosphere. The results illustrate significantly different sensitivity of these properties of the glassy phase to the cooling rate. The difference in crystallization behavior is also discussed. © 2012 Elsevier Ltd. All rights reserved.

The viscous flow behavior of Cu55Zr30Ti10Co5 metallic glassy samples was investigated on heating by a mechanical testing machine in accordance with the phase transformations taking place in the alloy. Phase transformations were studied by various methods, including differential calorimetry and electron microscopy. It was found that glassy samples demonstrated a relatively low viscosity of similar to 10(9) Pa s and did not lose their ability to be deformed under a relatively low stress of 5 MPa during the crystallization process until complete crystallization had occurred, thus producing in situ glassy/crystal composites. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Bulk metallic glasses attracted the attention of the materials research community after the breakthrough achieved from the end of the 1980s to the beginning of the 1990s. The high glass-forming ability (GFA) of some alloys allowed the formation of bulk metallic glasses upto about 80. mm in size by using various casting and water cooling processes. Owing to the absence of a crystalline lattice and defects such as dislocations, a unique deformation mechanism is realized in these materials, which thus exhibit high strength, high hardness, good wear resistance, and large elastic deformation. In this chapter, we describe the research achievements in the field of bulk metallic glasses and review their formation mechanism, GFA, structure, thermal stability, deformation behavior, corrosion resistance as well as their soft and hard magnetic properties. A special emphasis is given to ferrous metal-based soft magnetic Fe- and Co-based BMG alloys as well as hard magnetic Nd-based alloys. © 2013 Elsevier B.V.

A structural model for surface-enhanced stabilization in some metallic glass formers is proposed. In this model, the alloy surface structure is represented by five-layer Kagome-net-based lateral ordering. Such surface structure has intrinsic abilities to stabilize icosahedral-like short-range order in the bulk, acting as a cloak of liquidity. In particular, recent experimental observations of surface-induced lateral ordering and a very high glass forming ability of the liquid alloy Au49Ag5.5Pd2.3Cu26.9Si16.3 can be united using this structural model. This model may be useful for the interpretation of surface structure of other liquid alloys with a high glass forming ability. In addition, it suggests the possibility of guiding the design of the surface coating of solid containers for the stabilization of undercooled liquids.

We produce nanostructured metallic glasses in different metal-based glass-forming systems by using magnetron sputtering with powder targets. This new class of materials: nanograined metallic glasses (NGMGs) show unique mechanical, physical and chemical properties. Attributed to the surface nanostructural topography, Ti-based NGMGs exhibit enhanced cell proliferation, comparable to or even higher than the well known biocompatible Ti metals.

In-situ vitrification and crystallization of a PdCuNiP metallic glass was investigated using synchrotron light X-ray diffraction. Distinct differences between the Bragg peaks appearing upon thermal annealing of the glassy phase and those appearing during solidification from the melt were detected. This observation indicates that the crystal phases which are in competition with the amorphous phase during rapid quenching are not always the same with those precipitating upon annealing, contrary to a general believe. Measurements during in-situ vitrification allowed the determination of structural changes in the supercooled liquid and glassy states using real-space atomic pair PDF(r) and radial RDF(r) distribution functions. The first PDF peak corresponding to the first nearest neighbor (nn) coordination shell has a pre-peak at low interatomic distance (r) which grows during cooling from the liquidus temperature to the glass transition in the supercooled liquid region. A reversible expansion of the nn distances in the first coordination shell is observed in the same temperature range. Crystallization of shear bands operating under compressive applied stress previously observed by transmission electron microscopy has been non-destructively detected by synchrotron X-ray microscopy in transmission. Analysis of crystal nucleation frequencies under hydrostatic pressure shows that crystal nucleation is more favorable under compression loading.

(Ti-Zr)-(Cu-Ni-Co) bulk metallic alloys were investigated in the present work. Taking compositional formula (Ti-Zr)(49.5+x)(Cu-Ni)(49.5-x)Co-1 as a basis, we increased the content of Ti and Zr elements and decreased the content of Cu and Ni with the purpose of production of crystal-glassy composites. Such a kind of approach may allow combination of high strength of glassy alloys and good plasticity of crystalline alloys in these composite materials. According to this approach a large number of the alloys of different composition were prepared and investigated. Ti43.2Zr7.8Cu40.8Ni7.2Co1 bulk glassy-crystal composite sample showed the compressive strength of 1800 MPa and plasticity of about 5%. The effect of Y addition on the glass-forming ability and mechanical properties of the studied alloys was also investigated. (C) 2012 Elsevier Ltd. All rights reserved.

Here we report on the formation of a crystalline Au-based solid solution surface layer on solidification, which is responsible for yellow color of the Au-based bulk metallic glass (BMG) samples. The structure of the BMG alloy was studied by X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy. The deformation behavior of these Au-based BMG samples on heating was studied at temperatures above T-g at different strain rates. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4770072]

(Ti-Zr)-(Cu-Ni-Co) bulk metallic alloys containing 1000 mass ppm of boron were investigated in the present work. Taking compositional formula (Ti-Zr)(49.5 + x)(Cu-Ni)(49.5 - x)Co-1 as a basis, we increased the content of Ti and Zr elements and decreased the content of Cu and Ni with the purpose of production of crystal-glassy composites. Such a kind of approach may allow combination of high strength of glassy alloys and good plasticity of crystalline alloys in these composite materials. According to this approach a large number of the alloys of different composition and different diameters were prepared and investigated. Some of the prepared bulk glassy-crystal composite samples showes rather good properties: the compressive strength of 1800-2500 MPa and compressive plasticity up to 13.5%. (C) 2012 Elsevier B.V. All rights reserved.

This work deals with the tensile drawing behavior of poly(lactic acid) (PLA) in the amorphous state at room temperature. Nanomechanical mapping method is applied to obtain the submicrometer morphology together with mechanical properties using atomic force microscopy (AFM). By carefully collecting. the data of PLA specimens deformed with different elongation, we managed to monitor the microscopic structural/mechanical evolution simultaneously, and thus, the microscopic deformation mechanism was studied phenomenologically. The PLA matrix shows a highly heterogeneous response to the external stress. The stress is concentrated in some preferential places, thereby leading to high local Young's modulus and giving rise to crazes perpendicular to the tensile direction. However, in the position away from the crazes, the matrix undergoes no stress and shows similar Young's modulus as neat PLA specimens. The inhomogeneous stress distribution results in the catastrophic fracture of the matrix at an early state, which could explain the brittle nature of PLA at room temperature.

In order to stabilize the supercooled liquid and enhance the glass forming ability of Al-based glass forming alloy, the alloying design based on minor Ca substitution for Al was examined to retard the precipitation of face-centered-cubic (FCC) Al. Calcium was selected as the alloying element, because it has a large negative mixing heating with Al but a positive value with the other components. This is anticipated to facilitate formation of Al-Ca clusters and then inhibit the diffusion of Al atoms which is thought to be the dominant reason that limits the glass forming ability (GFA) of Al-based alloys. The proposed strategy was confirmed in experiments by the observation of a greatly increased reduced glass transition temperature, T-rg = T-g/T-l (T-g the glass transition temperature and T-l the liquidus temperature), the increased the activation energy for crystallization, and the increased activation energy for diffusion. The Al85-xY8Ni5Co2Cax (x = 0.5-5) system is found to possess extraordinarily high T-rg = 0.613 far exceeding that for any known Al-based glass forming alloys. (C) 2012 Elsevier Ltd. All rights reserved.

Structural and elemental mapping analyses were applied to characterize the mesostructure in the bulk metallic glass-forming Zr60FexCu30-xAl10 and Zr60+xFe5Cu25-xAl10 alloys. It is found that the observed meso-/microstructure is adjustable by the addition of Fe and tunes the acoustic anelasticity of the samples, while the relaxation time derived from our ultrasound measurements inversely scales with the mechanical properties and ductility of the alloys. The measurements also give data for the thermal diffusivity and coefficient of thermal expansion. Together with mechanical compression tests the results are further discussed on the basis of the thermo-elastic effect and the related role of heat dissipation on the propagation of shear bands in metallic glasses during plastic deformation. (c) 2012 Elsevier B.V. All rights reserved.

This article is devoted to in situ investigation of the Ni-based bulk metallic glass structural evolution and crystallization behavior by scanning tunneling microscopy/spectroscopy. The possibility of different surface nanostructures formation is shown by annealing of an original bulk glassy alloy in ultra high vacuum. Atomic locations in these surface nanostructures are completely different from those formed according to Ni-Nb binary phase diagram in the bulk area of the sample. The validity of the results is also verified by transmission electron microscopy and nano-beam diffraction measurements. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4760272]

Microwave processing of the Fe73Si7B17Nb3 metallic glass alloy powder was performed in a separated magnetic (H-) field by using a single mode 915 MHz microwave applicator. Rapid nanocrystallization was realized during microwave heating and a porous sintered sample with a diameter of 30 mm was produced using a loading pressure of 5 MPa. Cubic Fe and Fe3.5B phases were observed in the glassy matrix. Compared to conventional heating, microwave heating of the Fe73Si7B17Nb3 metallic glass powder exhibited the enhancement of crystallization kinetics. (c) 2011 Elsevier B. V. All rights reserved.

Investigation of glass-formation and crystallization processes of several alloys of Ag-Y-Cu system was conducted. The samples were produced by melt spinning and Cu-mold casting. The structure of ribbon samples was examined by X-ray diffractometry and transmission electron microscopy. Phase transformations were studied by differential scanning and isothermal calorimetry and differential thermal analysis. Despite the large difference in atomic radii between the components in the investigated system, even being produced by melt spinning technique at high cooling rate, only Ag61Y29Cu10 alloy with large supercooled liquid region was found to be X-ray amorphous. A principle for obtaining an alloy with high glass forming ability involving difference in atomic radii between the alloy components is considered. Efficient cluster packing model was also tested. (C) 2012 Elsevier B.V. All rights reserved.

In the present work we introduce a nanostructured low-alloy-type alpha + beta Ti-based alloy produced by tilt-casting method and subjected to subsequent thermo-mechanical treatment. It demonstrates good mechanical properties corresponding to high-alloy-type Ti-based alloys. After hot dual-axial forging at 900 degrees C Ti94Fe3Cu3 alloy, containing inexpensive alloying elements, showed a high ultimate tensile strength value of 1200 MPa and percentage elongation of 9%. It is shown that the intensive forging treatment is equivalent to severe plastic deformation and provides a nanostructured state (approximate to 50-100 nm crystal size) of the alloy leading to significantly improved mechanical properties even in low-alloys. (C) 2012 Elsevier B.V. All rights reserved.

The present work represents phase transformations observed upon cyclic loading of Zr62.5Fe5CU22.5Al10 bulk metallic glassy samples within reversible deformation regime prior to plastic deformation. The structure of the samples was studied by X-ray diffraction and transmission electron microscopy including high-resolution imaging and analysis of selected-area electron diffraction and nanobeam diffraction patterns. Thermal properties of the samples were characterized by differential scanning calorimetry. It is found that kinetically frozen anelastic deformation accumulates at room temperature and causes crystallization of metallic glassy phase forming precursors of metastable crystalline FCC Zr-based phase stabilized by the alloying elements. (C) 2012 Elsevier B.V. All rights reserved.

The outstanding efficiency of Fe-based metallic glass powders in degrading organic water contaminants is reported. While the glassy alloy contains 24% chemically inactive metalloid elements, the powders are capable to completely decompose the C32H20N6Na4O14S4 azo dye in aqueous solution in short time, about 200 times faster than the conventional Fe powders. The metastable thermodynamic nature and the particle surface topography are the major factors controlling the chemical performance of the metallic glass. Our findings may open a new opportunity for functional applications of metallic glasses.

The lack of new functional applications for metallic glasses hampers further development of these fascinating materials. In this letter, we report for the first time that the MgZn-based metallic glass powders have excellent functional ability in degrading azo dyes which are typical organic water pollutants. Their azo dye degradation efficiency is about 1000 times higher than that of commercial crystalline Fe powders, and 20 times higher than the Mg-Zn alloy crystalline counterparts. The high Zn content in the amorphous Mg-based alloy enables a greater corrosion resistance in water and higher reaction efficiency with azo dye compared to crystalline Mg. Even under complex environmental conditions, the MgZn-based metallic glass powders retain high reaction efficiency. Our work opens up a new opportunity for functional applications of metallic glasses.

We measured the temperature dependence of the apparent specific heat of Cu55Hf25Ti15Pd5 glassy alloy (metallic glass) by a differential scanning calorimetry method during continuous heating, and investigated the structural relaxation and crystallization processes. The results of structural evolution obtained by transmission electron microscopy are discussed in line with the differential scanning calorimetry data. Kinetics of crystallization process of the supercooled liquid above the glass-transition temperature is also studied. This alloy shows a complex relaxation and crystallization processes which are discussed in the paper. (C) 2011 Elsevier Ltd. All rights reserved.

Like non-metallic glasses, many bulk metallic glasses manifest a glass-transition temperature T-g during heating prior to crystallisation. While the exact nature of the atomic structure of a metallic glass depends on its thermo-mechanical history (quench-rate, plastic deformation, ... ), a unique and reproducible average atomic structure is attained if the glass transition temperature can be approached in a reversible manner. However, a metallic glass is always metastable and crystallises within a time t near or above its T-g in such a way that any reciprocal or real-space information on the fully glassy state at T &gt;= T-g must be completed within acquisition times tau(a) &lt;&lt; t and this condition is in general difficult to attain with conventional X-ray diffraction devices. Here we report on experiments using high-energy, high-flux synchrotron light in the transmission for probing of the atomic structure of bulk metallic glasses. Examples are given of the determination of the isochoric glass transition T-g and the quenched-in free-volume. Finally, we report on the evolution of the atomic structure in the supercooled liquid region (T &gt; T-g) and its role in the enhancement of glass formability. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

An Fe3O4 powder compact was irradiated with a 2.45 GHz microwave single-mode applicator at the magnetic field maximum position. Selectively heated regions (hot spot region) having several hundred micrometers to millimeter scale were formed. They exhibited metallic color. The SEM/EDX observations showed no appreciable difference in the compositions between the hot spot regions and the matrix. However, micro-XRD revealed that the hot spot region had a larger fraction of FeO than the matrix did, although the major consisting phase was Fe3O4 with a little Fe2O3. TEM observations indicated that the observed hot spot regions comprise these oxide phases separated in nano-sized grains, which agrees with our previous report. The larger fraction of FeO phase and flat surface might be related with the metallic color of the hot spot region. Their formation mechanisms and phase constitution were discussed. (C) 2011 Elsevier Ltd. All rights reserved.

Using the mixtures of the gas-atomized Fe-based glassy alloy powders blended with ceramic SiC particulates, toroidal shape Fe-based metallic glassy alloy composite cores were produced by the spark plasma sintering (SPS) process. The effect of the SiC particulates on the high frequency magnetic properties of the fabricated composite cores was investigated. The Fe-based metallic glassy alloy cores obtained by the SPS process exhibited high density and excellent soft magnetic properties. The addition of the SiC particulates was effective in improving high frequency magnetic properties. (C) 2011 Elsevier Ltd. All rights reserved.

Synchrotron-radiation studies allowed continuous acquisition of X-ray diffraction spectra for binary Pd81Si19 bulk metallic glass forming alloy in the glassy, crystalline and liquid state. Such an investigation allowed determination of structural changes in the liquid and glassy states using real-space radial RDF(R) and atomic pair PDF(R) distribution functions. Crystallization behavior of this alloy was also studied by conventional X-ray diffractometry, transmission electron microscopy and differential scanning calorimetry in isochronal and isothermal mode. (C) 2011 Elsevier Ltd. All rights reserved.

Results of long-term studies of the author are generalized and compared to works of other researchers of amorphous aluminum alloys and nanostructured materials obtained by crystallization of amorphous aluminum alloys and directly by cooling of the melt.

The glass-forming ability and devitrification behavior of a Zr(55)Cu(35)Al(10) bulk glass-forming alloy were examined to elucidate the very high nanocrystallization product density (&gt;10(23) m(-3)). The crystallization kinetics and structural changes in the glassy alloy were studied using X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. The observed sequential phase formation during isothermal reaction and the high nanocrystal density are consistent with the influence of residual oxygen even at low levels (&lt;500 ppm) to promote nucleation. (C) 2011 Elsevier B.V. All rights reserved.

A new Al 6061 alloy composite reinforced with [(Fe1/2Co1/2)(75)B20Si5](96)Nb-4 metallic glass was produced by sintering at a temperature between the glass transition (T-g) and crystallization temperature (T-x) of the metallic glass and close to the melting temperature of the Al alloy. At this temperature range (Delta T-x = T-x-T-g), the metallic glass particles exhibit viscous behavior, resulting in composites with low or zero porosity. The use of the glassy particles as reinforcement led to significant strengthening of the Al matrix alloy while retaining a plastic strain before fracture of about 13% leading to a remarkable combination of high strength and plasticity. Because metallic glasses are much harder than Al matrix alloys, when strain is applied to the composite, plastic deformation occurs in the matrix while the glassy particles deform only elastically. (C) 2011 Elsevier B.V. All rights reserved.

The aluminum-gold system exhibits various features that suggest high glass formability, such as a deep eutectic, formation of icosahedral clusters in the intermetallic compound near the eutectic minimum and a strongly negative heat of mixing. However, it is very difficult to form a glass with this system. Various issues related to glass formability are discussed using the Al-Au system as a negative test-case. In particular, the atomic level pressure was calculated from first principles for the first time for Al2Au, AlAu2 and AlAu4 intermetallic compounds. The atomic level pressure is very high in these compounds, suggesting frustrated electronic states which destabilize both crystalline and glassy phases.

Partial nanocrystallization induced by ion irradiation can be used to improve the surface properties in metallic glasses. We investigated the crystallization behavior and the structure of the formed nanocrystalline phases in a melt-spun Cu50Zr45Ti5 glassy alloy irradiated with 140 keV He ions to a fluence of 1.7 x 10(17)/cm(2). Crystalline nanoparticles were precipitated by He ion irradiation. The nanocrystalline phases were identified as a mixture of the orthorhombic Cu10Zr7 phase, tetragonal CuZr2 phase and monoclinic CuZr phase. Hardness enhancement was observed at a depth close to the projected range of the He ions, which was related to the formation of the crystalline nanoparticles. (C) 2011 Elsevier B.V. All rights reserved.

We report on the anelastic behavior of a cyclically loaded Zr(62.5)Fe(5)Cu(22.5)Al(10) bulk metallic glass well below its yield strength. The dynamic mechanical behavior of the glass is discussed on the basis of its structural and thermodynamic properties before and after tests. We show how the kinetically frozen anelastic deformation accumulates at room temperature and causes a structural relaxation and densification of the glass and further leads to its partial crystallization. (C) 2011 American Institute of Physics. [doi:10.1063/1.3655999]

We present the results of ultrahigh vacuum scanning tunneling microscopy/spectroscopy investigation of metallic glass surface. The topography and electronic structure of Ni63.5Nb36.5 have been studied. A great number of clusters with size about 5-10 nm have been found on constant current scanning tunneling microscopy images. The tunneling spectra of normalized tunneling conductivity revealed the energy pseudogap in the vicinity of Fermi energy. For energy values above 0.1 eV the normalized tunneling conductivity changes linearly with increasing of tunneling bias. The obtained results can be understood within suggested theoretical model based on the interplay of elastic electron scattering on random defects and weak intra-cluster Coulomb interaction. The effects of the finite edges of electron spectrum of each cluster have to be taken into account to explain the experimental data. The tunneling conductivity behavior and peculiarities in current images of individual clusters can also be qualitatively analyzed in the framework of suggested model.

Unlike crystalline materials, metallic glasses usually have a uniform structure without long-range periodicity and characteristic structural constituents. It has long been believed that no interfaces associated with separate grains can be found in metallic glasses. Here, we report on the successful synthesis of a gold-based nanograined metallic glass (NGMG) exhibiting a heterogeneously granular structure but possessing a glassy nature. The smallest particle size of the NGMG can be less than 10 nm. Having the advantage of the high surface area typical for nanostructures, the Au-based NGMG shows significantly enhanced catalytic activity. In addition, this NGMG sustains the good mechanical properties of metallic glasses, showing a high hardness of similar to 5.3 GPa. This work provides new insights into glass formation, offers the opportunity for further studies of the physical and chemical properties of this new type of non-crystalline solid, and promotes the applications of metallic glasses as catalysts, which may trigger intensive research in materials science. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

In order to achieve the large scanning angle without mechanical failure during actuation, the micro-mirror structure was fabricated using Fe-based metallic glass (MG) ribbon. High values of mechanical strength and elastic strain limit are desired for the torsion bar for providing high performance of the mirror, including large tilting angle and good stability. MG materials guarantee superior value of elastic strain limit and fracture toughness resulting from its amorphous structure without line defects like dislocations and grain boundaries. We chose Fe-base MG material for mirror actuation according to its good soft magnetic properties and simple structure without any further step of integration of magnetic material. Millimeter-size mirror device was successfully fabricated by laser machining techniques from Fe-based MG ribbon. Extremely large optical tilting angle of exceeding 100 degrees was obtained on activation of the mirror by magnetic force when electrical current of 100mA was applied. Large tilting angle of the mirror is due to the torsion bar which was fabricated with Fe-based MG material that has large elastic strain limit and high fracture toughness. (C) 2011 The Japan Society of Applied Physics

Metallic melts above the liquidus temperature exhibit nearly Arrhenius-type temperature dependence of viscosity. On cooling below the equilibrium liquidus temperature metallic melts exhibit a non-Arrhenius temperature dependence of viscosity characterized by liquid fragility phenomenon which origin is still not well understood. Structural changes and vitrification of the Pd42.5Cu30Ni7.5P20 liquid alloy on cooling from above the equilibrium liquidus temperature are studied by synchrotron radiation X-ray diffraction and compared with the results of first-principles calculations. Subsequent analysis of the atomic and electronic structure of the alloy in liquid and glassy states reveals formation of chemical short-range order in the temperature range corresponding to such a non-Arrhenius behavior. The first-principles calculations were applied to confirm the experimental findings. (C) 2011 American Institute of Physics. [doi:10.1063/1.3624745]

A novel Mg42U23CU25Y10 nanostructure-bcc ductile phase composite containing a Mg2Cu phase and amorphous zones has been obtained by injection casting. This alloy exhibits a large plastic engineering strain of 83% and plastic true strain of 177% with a flow stress at 4.3% deformation of 425 MPa. During compression, the deformation of the nanometer size bcc particles occurs by grain boundary sliding accommodated by flow controlled by grain boundary diffusion at room temperature. The hierarchical multiphase microstructure design allows for the operation and interaction of different shear deformation bands to provide large plastic strain at high strength. (C) 2011 Elsevier B.V. All rights reserved.

Using a single-mode 915-MHz microwave applicator equipped with a ceramic pressing unit, we processed the gas-atomized Cu50Zr45Al5 metallic glassy alloy powder blended with Sn powder of various contents in a separated magnetic (H-) field maximum. The blended powders were well heated in H-field. Bulk Cu50Zr45Al5 metallic glass matrix composites were produced with an applied pressure of 5 MPa. As a secondary phase, the Sn particle promoted the densification of the sintered samples.

The present work demonstrates the deformation behavior of Zr-Cu-Ni-Al bulk glassy alloys and Zr-Ni-Cu-Al-Pd glassy foils as well as Ni-Cu-Ti-Zr bulk crystal-glassy composites. Fracture of Zr(60)Cu(16)Ni(14)Al(10) and Zr(64.13)Ni(10.12)Cu(15.75)Al(10) bulk glassy alloys is featured by nearly equal fraction areas of cleavage-like and vein-type relief. The observed pattern of alternating cleavage-like and vein-type patterns illustrates a result of dynamically self-organizing shear propagation at the final catastrophic stage. The deformation behavior of Zr(64.13)Ni(10.12)Cu(15.75)Al(10) alloy has also been tested at LN(2) temperature. The strength of the sample decreases with temperature, and no clear serrated flow typical for bulk glassy samples tested at room temperature is observed in the case of the samples tested at LN(2) temperature. We also studied the deformation behavior of Zr-Ni-Cu-Al-Pd glassy foils thinned to electron transparency in situ in tension in a transmission electron microscope. We also present a Ni-Cu-Ti-Zr crystal-glassy composite material having a superior strength paired with a considerable ductility exceeding 10 pct. The metastable cP2 crystalline phase promotes a strain-induced martensitic transformation leading to pseudoelastic behavior as well as enhanced plasticity at room temperature. Underlying mechanisms of plastic deformation are discussed in terms of the interplay between the dislocation slip in the crystalline phase and the shear deformation in the glassy matrix.

The glass-forming ability of a Pd40Ni40Si4P16 alloy has been investigated. This alloy exhibits a wide supercooled liquid region of 107 K, a high reduced glass transition temperature of 0.596 and a small fragility parameter of 28, indicating that this alloy is a good glass former. Using flux treatment, the Pd40Ni40Si4P16 alloys can be easily produced as centimeter-scale metallic glasses. The glass transition and crystallization kinetics of this alloy were investigated by means of both differential scanning calorimetry (DSC) and differential isothermal calorimetry (DIC). Thermoplastic forming of the Pd40Ni40Si4P16 glassy alloy is easily performed due to the high thermal stability and low viscosity of the supercooled liquid. By pressing a "flat" silicon wafer onto a sample within the thermoplastic forming region, the surface of the Pd40Ni40Si4P16 metallic glasses could be significantly smoothened. The final surface showed a reduced root mean square roughness R (q) as low as similar to 2 nm. This indicates a simple approach to prepare "flat" surfaces for metallic glasses.

The elastic and viscoelastic properties of Zr65Ni10Cu5Al7.5Pd12.5 bulk metallic glass have been studied over a wide temperature and frequency range. In the amorphous state the mechanical response of the alloy is simple, similar to that observed in other bulk metallic glasses. In contrast, the phase-transformation process which occurs during annealing at elevated temperature induces a complex evolution. This alloy transforms to a supercooled liquid and then primarily forms an icosahedral phase followed by the formation of a mixture of crystalline phases. The mechanical properties in the amorphous state are well described using a physical model based on the concept of defects in amorphous materials. Atomic mobility is then governed by two parameters: activation energy U-el (0.92 eV) and correlation factor chi (0.39). The influence of the phase composition on the properties is discussed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The effect of serrations initiated in the elastic deformation region before macroscopic yielding on the mechanical behaviour of Zr(65)Fe(5)Cu(20)Al(10) bulk metallic glassy rods was analysed using a large number of samples. The apparent work-hardening-like behaviour and the plasticity tend to increase with the number of shear bands in the pre-yield region, which was analysed in terms of interaction with the shear bands generated during plastic deformation. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Metallic glasses are good candidates for applications in micromechanical systems. With size reduction of mechanical components into the micrometer and submicrometer range, the native surface oxide layer starts playing an important role in contact mechanical applications of metallic glasses. We use atomic force microscopy to investigate the wear behavior of the Ni62Nb38 metallic glass with a native oxide layer and with an oxide grown after annealing in air. After the annealing, the wear rate is found to have significantly decreased. Also the dependency of the specific wear on the velocity is found to be linear in the case of the as spun sample while it follows a power law in the case of the sample annealed in air. We discuss these results in relation to the friction behavior and properties of the surface oxide layer obtained on the same alloy. (C) 2011 American Institute of Physics. [doi:10.1063/1.3573778]

Owing to their low elastic moduli, high specific strength and excellent processing characteristics in the undercooled liquid state, metallic glasses are promising materials for applications in micromechanical systems. With miniaturization of metallic mechanical components down to the micrometer scale, the importance of a native oxide layer on a glass surface is increasing. In this work we use TEM and XPS to characterize the structure and properties of the native oxide layer grown on Ni(62)Nb(38) metallic glass and their evolution after annealing in air. The thickness of the oxide layer almost doubled after annealing. In both cases the oxide layer is amorphous and consists predominantly of Nb oxide. We investigate the friction behavior at low loads and in ambient conditions (i.e. at T = 295 K and 60% air humidity) of both as-cast and annealed samples by friction force microscopy. After annealing the friction coefficient is found to have significantly increased. We attribute this effect to the increase of the mechanical stability of the oxide layer upon annealing.

In this chapter we review a large set of the research results related to formation and characterization of bulk nanocrystalline and nanocomposite alloys produced by crystallization of an amorphous/glassy phase or directly from the melt on cooling. The formation of bulk glassy alloys and their processing routes are also outlined. Nanocrystallizing glassy samples leads to the formation of composites containing nanoscale crystalline or quasicrystalline particles. The structure, general physical, thermal, mechanical and magnetic properties of these nanostructured materials are discussed. Some of these composites possess a better combination of mechanical properties than those of fully glassy or crystalline alloys. For example, nanoscale crystalline and quasicrystalline phases play a very important role in ductilization of bulk glassy alloys. Nanostructured ferromagnetic alloys and glassy-nanocrystal composites possess good soft magnetic properties and create an important application area for such materials. © 2011 Woodhead Publishing Limited All rights reserved.

In situ vitrification in a synchrotron beam during cooling of a Pd42.5Cu30Ni7.5P20 melt allowed continuous acquisition of X-ray diffraction spectra in the supercooled liquid region between the liquidus temperature T-I and the glass transition temperature T-g for the first time in a metallic liquid alloy. These and subsequent acquisitions on reheating allowed determination of the structural changes in the supercooled and glassy states using the real space atomic pair distribution function PDF(R) and radial distribution function RDF(R). The nearest neighbor (NN) distance in the first coordination shell has a low R peak (pre-peak) that appears and increases on cooling from the liquidus temperature to the glass transition temperature in the supercooled liquid region. In this temperature range reversible expansion of the NN distances in the first coordination shell is observed. The slope of the expansion changes discontinuously at the glass transition. This behavior is explained by the theory of local topological fluctuations. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Large-size Ni-based bulk metallic glass (BMG) composite samples exhibiting simultaneously high strength, enhanced plasticity and improved conductivity were produced by spark plasma sintering of mixed glassy powder blended with high-conductive Cu particulates. This opens new possibilities for the applications of the BMG composites as functional and structural materials.

The temperature dependence of the elastic moduli was estimated from ultrasound time of flight measurements performed on bulk metallic glasses of composition Zr63-xCu24AlxNi10Co3. Using the corresponding values at the glass transition temperature, the local atomic strain was determined. The obtained values for the critical atomic strain calculated for 8 at% &lt; x &lt; 15 at% are close to the predicted universal criterion derived from a topological model, but may also reflect the difference in the chemical interaction that are not accounted by a topological approach.

The microstructure and mechanical properties of Al86Ni6Y6-xCo2Pd5 (x = 0, 0.5 and 1) rods, with a 1 mm diameter, have been investigated. The Al86Ni6Y6Co2 alloy consists of ductile fcc-Al and hard Al3Ni intermetallic phases embedded in the matrix. Replacing Y by Pd in the Al86Ni6Y6Co2 alloy promotes precipitation of additional crystalline phases, producing composite materials with tuneable mechanical behaviour. Compared to conventional Al-based crystalline alloys, the Al86Ni6Y6Co2 rod is relatively hard (395 HV) but exhibits a brittle behaviour when compressed at room temperature. The compressive plasticity increases to 1.5% in the Al86Ni6Y5.5Co2Pd0.5 alloy but the hardness decreases in this case. The plasticity, hardness and elastic properties of these alloys depend on the amount and intrinsic properties of the different constituent phases, as well as on the resulting microstructure obtained after the casting process (i.e., the size and shape of the precipitates). (C) 2010 Elsevier Ltd. All rights reserved.

The mechanical behavior and the kinetics of shear banding in bulk metallic glasses was investigated at room and liquid nitrogen temperature using the acoustic emission (AE) technique. It was demonstrated that the intensive AE reflecting the activity of strongly localized shear bands at room temperature vanishes at the transition of plastic flow from serrated to non-serrated with a reduction in temperature. The disappearance of AE clearly suggests that the shear band propagation velocity significantly decreases at low temperature, and sliding along the principle shear band is observed at the machine-driven rate. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Alloying addition, as a means of improving mechanical properties and saving on costs of materials, has been applied to a broad range of uses and products in the metallurgical fields. In the field of bulk metallic glasses (BMGs), alloying additions have also proven to play effective and important roles in promoting glass formation, enhancing thermal stability and improving plasticity of the materials. Here, we review the work on the role of alloying additions in glass formation and performance improvement of BMGs, with focus on our recent results of alloying additions in Pd-based BMGs.

Fe(36)Co(36)B(19.2)Si(4.8)Nb(4) bulk glassy rods were synthesized by copper mould casting. The effects of annealing treatments on the microstructure, elastic and mechanical properties of this alloy are investigated. Annealing below the glass transition temperature induces the formation of atomic clusters with pseudo-tenfold symmetry with a close relationship to the Fe(23)B(6) phase. Annealing at sufficiently high temperatures promotes the formation of stable Fe(2)B and FeB phases and Fe(Co) solid solution. The as-cast alloy exhibits ultra-high hardness (H &gt; 14 GPa), high reduced Young&apos;s modulus (E(r) &gt; 200 GPa) and good wear resistance. These properties are further enhanced after thermal treatments (H &gt; 18 GPa and E(r) &gt; 260 GPa are achieved in the fully crystallized sample). The mechanical hardening is accompanied with an increase of the elastic recovery and a decrease of the Poisson&apos;s ratio. The different microstructural mechanisms responsible for these annealing-induced changes in mechanical and elastic properties are discussed. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

In the present work we analyze the composition ranges over which bulk metallic glasses (BMGs) are produced in ternary, quaternary, and quinary amorphous alloys. The maximum diameter of the sample over which an amorphous structure can be retained, referred to as the critical diameter, D-c, is consistently large over specific composition ranges. For ternary BMGs, these most stable glasses are centered around the compositions, in decreasing order of accompanying D-c: A(44)B(38)C(18), A(44)B(43)C(13), A(65)B(25)C(10), A(56)B(32)C(12), A(55)B(28)C(17), A(70)B(20)C(10), and A(65)B(20)C(15). As a general trend, the most stable glasses have the lowest concentrations of solvent atoms. Structural analysis using the efficient cluster packing model suggests that the best ternary glasses are near the isostructural composition, which represents the maximum degree of atomic confusion. Both D-c and Delta T-x=T-x -T-g, the difference between the crystallization and glass transition temperatures, are larger in quaternary and quinary systems relative to typical values for ternary BMGs. Glass-forming ability increases with complexity of the alloy, i.e., increasing number of alloying elements. The above results shed some light not only on compositional dependence of the formation of glassy phase but also its relation to the structure of the glasses. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506687]

Using a mixed powder of gas-atomized Cu50Zr45Al 5 glassy alloy powder blended with Cu particulate, we fabricated bulk Cu50Zr45Al5 glassy alloy composite (GAC) by a spark plasma sintering (SPS) process. The fabricated Cu50Zr 45Al5 GAC specimens exhibit simultaneously high strength and improved plasticity as well as dramatically improved electrical conductivity by adding high-conductive Cu particulate. No crystallization of glassy matrix and good bonding state between the particles are responsible for good mechanical and electrical properties of the fabricated bulk GACs. © 2010 Elsevier Ltd. All rights reserved.

The elastic and damping behaviors of porous Zr55Cu30Al10Ni5 glassy alloy fabricated by a spark plasma sintering (SPS) process were investigated as a function of porosity at room temperature. Bulk modulus (K) and Lame parameter (lambda) decrease in a parabolic manner, while Young&apos;s (E) and shear (G) moduli decrease gently with an increase in porosity. The order of K, lambda, E, and G, which is monopolistically characteristic of nonporous glassy alloys, changes to the order of E, K, G, and lambda, reflecting a crystalline-like deformation mode which is further confirmed by combining the decrease in Poisson&apos;s ratio with the increase in G/K and E/K ratios up to 34.4% porosity. An increase in porosity induces frequency convergence for longitudinal wave, as well as increases in the longitudinal and shear attenuation coefficients. (C) 2010 Elsevier Ltd. All rights reserved.

A new Pd79Au1.5Ag3Si16.5 bulk metallic glass was successfully synthesized in a maximum casting thickness range to 3 mm. Upon heating, the single glassy phase decomposed into Pd-rich crystalline phases and a Si-rich amorphous phase due to solute partitioning. In addition to high thermal stability, this bulk glassy alloy also exhibited a high degree of ductility and excellent corrosion resistance, showing potential applications as biomaterials.

In order to uncover the mechanism of fluxing-enhanced undercooling, a study of the liquid structure in a Pd40Ni40Si4P16 bulk-glassy alloy was performed, which revealed that a flux-treated sample presents a shortened mean interatomic distance and an Increased coordination number within the first shell, which results in a more densely packed local structure than in an unfluxed sample. In addition to the usual influence of fluxing to effect a deactivation of nucleation catalysts to yield enhanced undercooling, structural studies have discovered a new effect of fluxing The local structural change induced by fluxing is associated with an increase in the delay time for the onset of nucleation. The prolonged transient period is also reflected by sluggish atomic transport in the fluxed sample, which promotes kinetic stability of the undercooled (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd All rights reserved.

The mechanical behaviour of Mg(65-x)Li(x)Cu(25)Y(10) (x = 9, 14 and 19) metallic glass composites has been studied. For 9 and 14 at.% Li the alloys exhibit a brittle behaviour. The microstructure of the alloy containing 9 at.% Li consists of a bcc Mg-Li solid solution phase embedded in an amorphous phase. Higher concentrations of Li promote the formation of the bcc phase, Mg(2)Cu and also a small volume fraction of Y-containing intermetallic. The alloy with the highest Li content, i.e. 19 at.%, exhibits a compressive engineering strain of 25%. The hierarchical microstructure design with multiphase components allows for the operation and interaction of different deformation behaviour to provide for useful levels of plastic deformation. (C) 2010 Elsevier B.V. All rights reserved.

This paper reports on the unusual solidification behavior of Zr55Cu30Al10Ni5 bulk glassy alloy produced using low-purity Zr in which both primary and eutectic-type structural constituents were formed simultaneously during solidification of the melt. Additionally, two different types of primary crystalline phases were observed. One of them was cF96 and contained all the four constituent elements. Reasons for these observations have been related to the presence of impurities in the alloy leading to inhomogeneous nucleation and consequent modification of the crystallization behavior. The structure and thermal stability of the samples were studied using X-ray diffraction, scanning and transmission electron microscopy, as well as differential scanning calorimetry methods. Although the cast alloys made with low-purity Zr showed somewhat decreased glass-forming ability, their mechanical strength was still high. (C) 2010 Elsevier Ltd. All rights reserved.

New Ni-rich Ni-Pd-P-B bulk glassy alloys with high glass-forming ability were formed by water quenching. The Ni60Pd20P17B3 and Ni65Pd15P17B3 alloys possess high corrosion resistance in 1N H2SO4 and 3 mass% NaCl solutions. In both solutions, their corrosion resistance decreases with increasing Ni content in the alloys. The origin of high corrosion resistance for the Ni60Pd20P17B3 alloy in the corrosive solutions is explained by formation of the Pd-enriched sub-surface layer, which is able to protect the alloy against the corrosion. (C) 2010 Elsevier B.V. All rights reserved.

This manuscript explores the influence of atomic structure on glass forming ability and thermal stability in binary metallic glasses. A critical assessment gives literature data for 628 alloys from 175 binary glass systems. The atomic structure is quantified for each alloy using the efficient cluster packing model. Comparison of atomic structure with amorphous thickness and thermal stability gives the following major results. Binary glasses show a strong preference for discrete solute to solvent atomic radius ratios R*, which give efficient local atomic packing. Of 15 possible R* values, only five are common and only four represent the most stable glasses. The most stable binary glasses are also typically solute rich, with enough solute atoms to fill all the solute sites and roughly one-third of the solvent sites. This suggests that antisite defects, where solutes occupy solvent atom sites, are important in the glass forming ability of the most stable glasses. This stabilising effect results from an increase in the number of more stable solute-solvent bonds in solute rich glasses. Solute rich glasses also enable efficient global atomic packing. Together, these structural constraints represent only a narrow range of topologies and thus give a useful predictive tool for the exploration and discovery of new binary bulk metallic glasses (BMGs).

We studied Cu-Zr-based alloys having exceptionally high glass-forming ability (GFA) and investigated the influence of Ag and Al addition on their structure and crystallization behavior. Most of the bulk glassy alloys (BGAs) do not contain any crystals, while some samples studied by high-resolution transmission electron microscopy (HRTEM) were found to contain well-developed medium-range order zones and nanoparticles in a bulk form. The crystallization kinetics of Cu55Zr45, Cu50Zr50, Cu55-x Zr45Ag (x) (x = 0, 10, 20), Cu45Zr45Al5Ag5, Cu44Ag15Zr36Ti5, and Cu36Zr48Al8Ag8 glassy alloys was analyzed. An influence of the cooling rate on the formation of glassy phase and thermal stability of the Cu-based glassy alloys on heating was also studied. The crystallization kinetics and phase composition of the ribbon-shape and bulk glassy samples of Cu36Zr48Al8Ag8 alloys were also analyzed. The results also indicate that the best glass-forming compositions are possibly located at slightly off-eutectic area, owing to the shift of the eutectic point due to the nonequilibrium processing conditions.

Using a gas-atomized Ni(59.35)Nb(34.45)Sn(6.2) metallic glassy alloy powder blended with Sn powder of various contents, Ni-Nb-Sn bulk metallic glassy matrix composites were fabricated by a microwave (MW)-induced sintering process in a single-mode 2.45 GHz MW applicator in a separated magnetic field. The Ni(59.35)Nb(34.45)Sn(6.2) glassy alloy powder and its mixed powders containing Sn particles could be heated well in the magnetic field. The addition of Sn particles promoted densification of the sintered Ni(59.35)Nb(34.45)Sn(6.2) metallic glassy powder. Bulk samples without crystallization of the glassy matrix and with good bonding state among the particles were achieved at a sintering temperature of 833 K.

Using real space pair distribution functions derived from high precision x-ray diffraction data, the local atomic structure of Zr-Ni and Zr-Ni-Al metallic glasses was investigated. Unlike Zr-Cu metallic glasses, the structure of Zr-Ni metallic glasses cannot be approached with an ideal solution model, due to strong attractive interactions between Zr and Ni atoms, which promote chemical short range order. Addition of Al can be beneficial for the glass forming ability of Zr Ni metallic glasses. The atomic size of Al, being intermediate to those of Zr and Ni and the strongly attractive interactions between Zi-Al and Zr Ni atoms can lead to highly negative volumes of mixing Delta V-mix, and to denser atomic structures, reduced atomic mobility in the liquid and easier suppression of crystallization in the undercooled liquid state (C) 2010 American Institute of Physics. [doi:10.1063/1.3446131]

The temperature dependence of length change and viscous flow of the Cu36Zr48Al8Ag8 glassy alloy is examined in both the glass transition and supercooled liquid regions. Moreover, this alloy is found to exhibit phase separation rather by binodal mechanism in the glassy phase prior to crystallization. There is an apparent decrease in viscosity observed upon crystallization that is connected with the densification of the sample, but the intrinsic viscosity does not rise significantly until the initial crystallization process is almost complete. During the process the partly crystallized supercooled liquid still behaves like a fluid until a large fraction of the crystalline phase (similar to 90%) is formed. This new insight on flow behavior opens up possibilities for innovative processing of precise bulk shapes with high nanocrystal densities. (C) 2010 Elsevier Ltd. All rights reserved.

Using the mixed powders of the gas-atomized Ni-based metallic glassy alloy powder blended with metal W or ceramic SiC particulates, we fabricated large-size bulk glassy alloy composites (GACs) by a spark plasma sintering (SPS) process. The microstructure and mechanical properties of the prepared GAC specimens were investigated, and the effect of addition amount of the crystalline particulates on the properties of the sintered GAC specimens was discussed. The Ni-based bulk GACs with ultrahigh strength and enhanced plasticity were produced. The improvement of plasticity of the fabricated bulk GACs is attributed to the structural inhomogeneity caused by the addition particulates inclusion. The optimum content of the crystalline particulates is about 5-10 vol.%. (C) 2009 Elsevier Ltd. All rights reserved.

A novel Mg46Li19Cu25Y10 nanostructure-bcc ductile phase composite containing a Mg2Cu phase and amorphous zones has been obtained. The large plasticity (25%) under compression is due to the soft bcc Mg-Li solid solution phase and the large Mg2Cu phase particles. A three stage serrated flow pattern is observed in the compressive stress-strain curve which is associated to the microcrack development. (C) 2009 Elsevier Ltd. All rights reserved.

The Poisson's ratio of Zr-based bulk metallic glasses in the system Zr(63-x)Cu(24)A(lx)Ni(10)Co(3) was found to exhibit a non-monotonous behavior as a function of x when measured with ultrasound by the pulse-echo technique. In addition, from wave propagation velocity measurements at different frequencies, i.e. f = 2.25 MHz and f = 10 MHz, a composition-dependent anelastic behavior as a function of x is found, exhibiting a similar non-monotonous behavior. In this work we further investigated the plastic deformation and the creep properties of this glass system in compression tests and by nanoindentation. The plastic strain and the measured creep deformation show correlations with the Poisson's ratio. We then discuss the anelastic behavior observed while measuring the sound-wave propagation velocity in the frame of the thermoelastic damping and the bond reorientation as proposed by Egami. Finally we discuss these effects with regard to X-ray diffraction analysis. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Glass-transition region is still a somewhat "dark area" in the field of materials science. In order to shed more light on this phenomenon, the glass-transition behavior was studied in a Zr(55)Cu(30)Al(10)Ni(5) glassy alloy by monitoring its specific-heat capacity measured using a differential scanning calorimeter during heating in a step-scan mode. This reduces the influence of kinetic effects which shield the transition. It is suggested that two types of relaxation (likely related to the diffusivities of different alloying elements Cu and Ni on the one hand as well as Zr and Al on the other hand) take place and compete in the glass-transition region.

This paper presents a systematic study on the structure, phase composition, strength and hardness of the rapidly solidified Mg(100-2x)Cu(x)Y(x) alloys. Their structure mostly consists of relatively large dendritic grains of hcp-Mg phase and smaller grains of CuMg(2) phase. Nano-particles of CuMg(2) phase were also observed as a result of decomposition of the supersaturated Mg-solid solution. As in the Mg(98)Cu(1)Y(1) alloy studied earlier some fraction of the glassy phase was observed in the studied alloys and the volume fraction of the glassy phase increases with increase in Cu- and Y-content. Yield stress and Vickers microhardness values in general increase with increase in the solute content and reach a saturation at x = 4-5. (C) 2010 Elsevier B.V. All rights reserved.

We report that clearly different microstructures were obtained corresponding to different parts in a Pd40Ni40Si5P15 glassy rod, showing a nature of structural flexibility of a glass. Such a structural difference was believed to have the origin in the different cooling rate induced by the solidification in succession of the molten alloy during the casting. Upon this difference in the microstructure, the samples show very different deformation behaviors. [doi: 10.2320/tnatertrans.M2009274]

This paper reports a novel class of Zr-Cu-Fe-Al bulk metallic glasses (BMGs) with high Zr content and unusual deformation behavior. Higher content of Zr results in lower hardness, but favors the generation of highly localized shear bands, even if nanocrystalline phases precipitate in the glassy matrix. Moreover, flow of the dominant shear band proceeds slowly under compressive stress without rapid shear rupture and facture. The unusual deformation behavior suggests that designing BMG with a high content of solvent element and low hardness might be a promising new way of developing ductile BMG. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Using a single mode 915 MHz applicator, we fabricate novel Cu(50)Zr(45)Al(5) metallic glass/polyphenylene sulfide (PPS) composites with high relative densities by microwave processing the constituents in a separated H-field with an applied pressure of about 5 MPa. The heating behaviors and structural changes of the composites have been investigated. A good bonding state between metallic glassy and PPS particles is found. The gradient structure is also induced by microwave heating of the composites with a high fraction of PPS phase. (C) 2009 Elsevier B.V. All rights reserved.

In this paper, we report on significantly enhanced plasticity in addition to improvement of thermal stability in Pd40Ni40Si4P16 bulk metallic glass (BMG) by flux treatment. With fluxing, the plastic strain was remarkably enhanced from approximately 3% to up to 52%, which likely correlates with a larger volume of shear transformation zones. It is suggested that the flux treatment is not only a good approach to improve the thermal stability but may be a promising way to enhance the plasticity of BMGs. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

This paper presents a study of the deformation behaviour of a glassy phase in two Zr-based alloys, Zr(65)Ni(10)Cu(5)Al(7.5)Pd(12.5) and Zr(65)Al(7.5)Ni(10)Pd(17.5), performed in situ in a transmission electron microscope. In contrast to the case of shear localisation and formation of 10-20 nm thick shear bands in deformed bulk glassy samples studied earlier, it is found that in thin (electron-transparent) samples the glassy phase in front of a crack deforms more homogeneously and no nanocrystallisation takes place. The reasons for such behaviour are discussed. According to the observed results, one can conclude that the studied metallic glasses can be intrinsically ductile in submicrometre-sized volumes.

We report on the glass-forming ability and devitrification behavior of Zr60Cu30Al10, Zr60Cu25Al10Fe5 and Zr62.5Cu22.5Al10Fe5 bulk glass-forming alloys on heating. The effect of Fe addition on the structure of Zr-Al-Cu alloys is also discussed. Crystallization kinetics and structural changes in the glassy alloys were studied using X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. The results indicate that good glass-formers, such as Zr62.5Cu22.5Al10Fe5, are located somewhat beyond the equilibrium eutectic point. Possible phase separation in the supercooled liquid on heating and electron beam-induced in situ crystallization are observed and discussed.

A new series of bulk metallic glasses were developed by addition of Fe into the ternary Zr60Cu30Al10 alloy. Although Fe-Cu element pair shows distinct immiscibility with a large positive heat of mixing, substitution of Fe for Cu significantly improves the glass-forming ability of the ternary Zr60Cu30Al10 alloy. The critical diameter for glass-formation increases from 8 mm for Zr60Cu30Al10 alloy to 20 mm for Zr60Cu25Fe5Al10 and Zr62.5Cu22.5Fe5Al10 alloys. As compared with the ternary Zr60Cu30Al10 alloy, the new quaternary Zr-Cu-Fe-Al alloys show lower liquidus temperatures. The Zr60Cu25Fe5Al10 and Zr62.5Cu22.5Fe5Al10 alloys, the best BMG-formers in this alloy system, are found to locate very near a Zr-Cu-Fe-Al eutectic point. The new Zr-Fe-Cu-Al bulk metallic glasses exhibit high strength of about 1700 MPa. The plastic strain increases from 7.8% to 11.3% with increasing the content of Fe from 0 to 12.5%. The finding of a Ni-free Zr-based bulk glassy alloy with the extremely high glass-forming ability is expected to extend the future application of bulk metallic glasses.

We studied Cu-Zr-based alloys having exceptionally high glass-forming ability (GFA), and investigated the influence of Ag and Al on the GFA and crystallization behavior. Most of the bulk glassy alloys studied do not contain any crystals in the as-solidified state. The crystallization kinetics of Cu55Zr45, Cu50Zr50, Cu55-xZr45Agx (X = 0, 10, 20), Cu45Zr45Al5Ag5, Cu55Zr30Ti10Ag5, Cu55Hf25Ti15Ag5, Cu44Ag15Zr36Ti5 and Cu36Zr48Al8Ag8 glassy alloys was analyzed. Cu35Zr45Ag20 alloy exhibits possible phase separation upon heating within the supercooled liquid region prior to crystallization. The depletion of Ag in the residual glassy phase results in the higher thermal stability of Cu35Zr45Ag10 versus Cu35Zr45Ag20. Cu50Zr50 undergoes primary crystallization, forming a metastable monoclinic CuZr phase, while Cu55Zr45, Cu45Zr45Ag10 Cu35Zr45Ag20 and Cu45Zr45Ag20 and Cu45Zr45Al5Ag5 undergo eutectic crystallization, forming mostly stable phases. Cu50Zr50, Cu55Zr30Ti10Ag5 and Cu55Hf25Ti15Ag5 undergo nanocrystallization. Although some differences in the crystallization behavior between Cu55-xZr45Agx, (x = 0, 10, 20) and Cu45Zr45Al5Ag5 were found, this may not be the only reason Al and Ag additions improve the GFA of the Cu-Zr alloy. The difficulty in nucleating the tP4 AgZrss phase may be responsible for the high glass-forming ability of the Cu36Zr48Al8Ag8 and Cu44Ag15Zr36Ti5 alloys.

Sub-nanometer size cF8 Ge clusters are found to be homogeneously distributed within the Si-Mn amorphous matrix of the SiGeMn thin films deposited by sputtering technique on silicon substrate. The existence of such clusters is observed by XRD and TEM. The electrical conduction in such a composite film seems to be governed by the variable range hopping. Such a two-phase semi-conductive composite material with nearly atomic-scale phase separation may be considered as a suitable functional material for nano-electronics and nano-electromechanical systems.

Compression testing shows that at low-oxygen levels (240 ppm) the Cu(49)Hf(42)Al(9) glass deforms predominantly by shear and is quite tough. Specimens with higher oxygen levels (1700 ppm) have oxygen-containing dendrites in an amorphous matrix and show no plasticity. Importantly, the dominant fracture mode is not shear but local tensile failure. Although there is a slight reduction in the toughness of the glassy matrix, the severe embrittlement is primarily because of the brittle dendrites that facilitate crack initiation and propagation. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A microscopic model is presented, which describes the sintering of equal-sized spherical particles that differ in phase. A wetting phase diagram of sintering was developed that classifies the equilibrium shapes that can arise during sintering of two spheres with different surface energies. The formation and growth of the interface between the dissimilar phases was studied from the point of view of solid-state wetting. The three-dimensional computer simulation of interface-reaction-controlled sintering was conducted using the Surface Evolver program. The deviation of dynamic contact angle from its equilibrium value was proportional to the contact line velocity and inversely proportional to the triple junction mobility. The stability of particle cluster configuration in equilibrium was also examined using Cahn&apos;s concept on grain-boundary energy ratios in two-phase materials.

We investigated the microstructure, in particular, the interface structure between powder particles in the Ni(52.5)Nb(10)Zr(15)Ti(15)Pt(7.5) bulk glassy alloy composites containing 10 vol.%SiC particulates prepared by a spark plasma sintering (SPS) process by means of scanning and transmission electron microscopies. The SiC particulates were dispersed homogeneously in the Ni(52.5)Nb(10)Zr(15)Ti(15)Pt(7.5) glassy matrix. No crystallization of the Ni(52.5)Nb(10)Zr(15)Ti(15)Pt(7.5) glassy alloy took place during the SPS process. The good bonding states between SiC particulates and glassy matrix, as well as between glassy particles were recognized. No intermediate layer in the bonded interfaces was observed. (C) 2008 Elsevier B.V. All rights reserved.

Metallic glasses exhibit low viscosity in a temperature range between the glass-transition and crystallization temperature which allows successful sintering of glassy powders. Microwave heating being a volumetric heating has significant advantages over conventional heating in materials processing, such as substantial energy savings, rapid heating rates and process cleanness. In the present study, we investigate the stability of the Fe(73)Si(7)B(17)Nb(3), Fe(65)Co(10)Ga(5)P(12)C(4)B(4), Ni(52.5)Zr(15)Nb(10)Ti(15)Pt(7.5), Ni(60)Nb(20)Ti(15)Zr(5), Zr(55)Cu(30)Al(10)Ni(5) and Ti(47.5)Zr(10)Cu(30)Pd(7.5)Sn(5) glassy powders and formation of the porous bulk metallic glassy samples by microwave heating in a single-mode cavity with separated electric (E) and magnetic (H) field maxima in an inert atmosphere. The Fe(73)Si(7)B(17)Nb(3) and Fe(65)Co(10)Ga(5)P(12)C(4)B(4) alloys crystallized upon MW heating in both E- and H-field maxima forming a nanostructure. The Ni(52.5)Zr(15)Nb(10)Ti(15)Pt(7.5) and Zr(55)Cu(30)Al(10)Ni(5) alloys were heated well in H-field and were not heated well enough in E-field. In case of Ni(52.5)Zr(15)Nb(10)Ti(15)Pt(7.5) and Ni(60)Nb(20)Ti(15)Zr(5) alloys sintered samples were obtained. (C) 2008 Elsevier B.V. All rights reserved.

The crystallization kinetics and structure changes in a melt-spun Cu50Zr45Ti5 glassy alloy on heating were investigated by X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and differential isothermal calorimetry. The glassy phase in the Cu50Zr45Ti5 alloy was crystallized forming Cu10Zr7 and CuZr2 phases upon thermal annealing. The activation energy for crystallization obtained by the Arrhenius equation was 435 kJ/mol. The crystallization process took place by nucleation and growth mechanism, and an Avrami exponent of about 3.3 may indicate a three-dimensional interface-controlled growth of nuclei with a decreasing nucleation rate. (C) 2008 Elsevier B.V. All rights reserved.

Two-phase bulk metallic glasses (BMGs) have attracted increasing interest since phase separation might produce metallic glasses with new physical and mechanical properties. In this study, we fabricated the dual phase glassy BMG composites by a spark plasma sintering process using a mixed powder of the gas-atomized Ni-based and Fe-based metallic glassy alloy powders. The thermal stability, microstructure, mechanical and magnetic properties of the obtained dual-phase glassy composites were investigated. The dual-phase glassy composites exhibited ultra-high strength and good soft magnetic properties which satisfy large-size requirements. (C) 2009 Elsevier Ltd. All rights reserved.

This paper presents some crystalline structures which can be taken as the approximants of the corresponding metallic glassy phases. Such phases have a Clustered structure and preferably (but not strictly necessarily) a large unit cell. Peak intensities of their radial distribution functions (RDFs) must be integrated at a step of about 0.01 nm in order to obtain RDFs similar to those of the corresponding glassy alloys owing to a degree of disorder related to the corresponding glassy structures. (C) 2008 Elsevier Ltd. All rights reserved.

The influence of a minor Si addition oil the glass-forming ability and mechanical properties of Pd40Ni40P20 alloy was investigated. It is suggested that the minor Si addition can adjust the composition to be closer to eutectic, which favors a large undercooling. Furthermore, Si addition led to an enhancement in the ductility of Pd-Ni-P bulk metallic glasses. Simultaneously it is of great interest that there are nanoscale and microscale wavy steps observed on the fracture surface of Pd40Ni40Si4P16 metallic glass. It is Suggested that a quickly running crack dissipates excess energy in terms of stress wave, leaving Such wavy traces oil the fracture surface of the deformed Pd-based metallic glass. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

To investigate the microwave (MW) processing of Fe(3)O(4), for which occurrence of decrystallization has been reported, the micro/nanostructures of MW-heated Fe(3)O(4) powder were observed in this study. The specimens were irradiated by 2.45 GHz MW at the position of magnetic (H)-field maximum in a TE10 single mode applicator. The specimen was heated well above the Curie temperature in H-field. The heated specimen above 1000 degrees C revealed the glass-like surface with the diminished x-ray diffraction (XRD) peak intensities. They resemble the reported features of decrystallization in an earlier work performed at Penn State University. According to the XRD profiles of the MW-heated specimens, formation of FeO and shift of Fe(3)O(4) peaks to the lower angle with the broadened width were observed. To account for the findings, a model is presented that phase separation occurred into FeO and Fe(3)O(4) resulting in an increased lattice parameter due to the increased oxygen content. This activity is caused by local transport of oxygen in nanoscale. Considering the shape of the main XRD Fe(3)O(4) peak with a shoulder and the existence of halo in nanobeam diffraction (NBD), amorphous phase areas exist. As a result of transmission electron microscopy observation, it was shown that they were in nanoscaled localized regions, and it was not confirmed that the glass-like morphologies (or decrystallized morphologies) are totally amorphous. The observed micro/nanostructures and mechanism of the amorphous phase formation were discussed considering the Fe-O phase diagram.

The crystallization behavior of melt-spun ribbons and bulk samples of the Cu36Zr48Al8Ag8 glassy alloy on heating is presented here. The crystallization kinetics and structural changes in the Cu36Zr48Al8Ag8 glassy alloy were studied using x-ray diffraction, transmission electron microscopy, differential scanning, and isothermal calorimetry methods. A clear comparison is made of the differences in the crystallization kinetics of the melt-spun ribbons and the copper-mold-cast bulk rod samples. It was suggested that the kinetics of crystallization in the rod sample, at any given temperature, are somewhat different than in the ribbon samples, probably because of size and free volume effects. Differences in the crystallization behavior of this alloy with other Cu-Zr-Al-Ag alloys have also been discussed.

The atomic structure of Zr-Cu binary amorphous alloys was studied using real space pair distribution functions derived from x-ray diffraction. The structure can be modeled by an ideal solution approximation because of relatively weak Cu-Zr atomic interactions. Addition of Al to Zr-Cu metallic glasses modifies the atomic structure in the short and medium range order because of the strongly attractive interaction between Al and Zr atoms. These interactions generate strong deviations from the ideal solution behavior.

Microwave (MW)-induced heating and sintering was carried out by a single-mode MW applicator in a separated electric field or magnetic field using the gas-atomized Ni52.5Nb10Zr15Ti15Pt7.5 metallic glassy alloy powder blended with various contents of Sn powders. The addition of Sn particles was found to promote the densification of the sintered Ni-based metallic glassy powders. With increasing Sn contents, the sintering temperature to obtain bulk sample with the retention of the glassy structure was reduced, and good bonding between powder particles was achieved. © 2008 Elsevier Ltd. All rights reserved.

The structure and mechanical properties of Ti-Fe-B and Ti-Fe-Co-B alloys produced in the shape of the arc-melted ingots of about 25 mm diameter and 10 mm height are studied. The hypereutectic alloys showed excellent compressive mechanical properties. The structures of the high-strength and ductile hypereutectic alloys studied by X-ray diffractometry and scanning electron microscopy were found to consist of the primary cubic cP2 intermetallic compound (TiFe-phase or a solid solution on its base) and a dispersed eutectic consisting of this cP2 intermetallic compound + BCC cI2 beta-Ti supersaturated solid solution phase. The addition of B increased mechanical strength. Si causes embrittlement owing to the formation of alternative intermetallic compounds. The structure and deformation behaviour were studied. (C) 2008 Elsevier B.V. All rights reserved.

In the present study, we report the formation of the Mg-based bulk metallic glass (BMG) samples by spark plasma sintering of the amorphous powders prepared by ball-milling. The sintering was performed in the supercooled liquid region (T-g - T-x) and fully glassy Mg-based samples were successfully sintered at 398 K. The deformation on the surface associated with Vickers indentation hardness tests of the compacts reveals the presence of the semi-circular shear-bands around the indents and also reveals inhomogeneous nature of plastic deformation. [doi: 10.2320/matertrans.MRA2008177]

We report on the atomic structure via pair distribution function (PDF) analysis of metallic glasses of the Zr-Cu-Al and Zr-Ni-Al families. The PDFs were evaluated from the X-ray diffraction data. Transmission X-ray diffraction spectra of the investigated samples were measured using monochromatic, high-energy synchrotron radiation. In this work we demonstrate the effect of composition on the pair distribution functions. A variation of first PDF peak shape was observed on modification of Cu and Al content. A split of the first PDF peak was found to be more pronounced in Zr-Ni-Al than in Zr-Cu-Al glasses suggesting differences in their atomic structures. (c) 2008 Elsevier B.V. All rights reserved.

The authors report the observations of nanoscale wavy steps on fracture surface of a Pd-based bulk metallic glass. The wavy steps are generated by crack front waves. Besides this kind of steps, it is also found that there is a dispersive microscale wavy trace aligned along a backbone "branch line," which is induced by dynamic instability of a rapidly propagating crack front. Such microbranching events are evidenced as dissipating energy accumulated at the crack front by creating the additional fracture surface area when the crack propagation exceeds a critical velocity.

Owing to so-called skin-effect bulk metals reflect microwaves (MWs) and can hardly be heated. They can undergo only surface heating due to limited penetration of the MW radiation. Whereas metallic powders can be penetrated into itself and absorb such radiation and efficiently heat. So, in the present work, we theoretically studied the MW penetrating mechanisms, the possible MW heating mechanisms of metallic powders and provide some theoretical explanation of the MW penetrating and MW heating behavior.

It is known that bulk metallic samples reflect microwaves while powdered samples can absorb such radiation and be heated efficiently. In the present work we studied mechanisms of microwaves absorption of the metallic powders from three-layered particles. The present paper shows dependence of the effective permittivity from the volume fraction of particles and from the thickness of shell for different volume fraction of particles. Also we show the distribution of heat absorbed inside the plate from the composite plate.

The electromagnetic field distributions in the waveguide of a 915MHz single-mode microwave sintering applicator equipped with a loading pressure system were simulated using a JMAG-Studio program. The disturbance in the magnetic field as well as in electric field was caused by the insertion of the alumina loading pressure system due to reflection effect of alumina. However, the separated magnetic field and electric field maxima can be obtained by adjusting position of the alumina loading pressure system in the waveguide. The simulation results were evaluated by comparison with experimental measurement.

Microwave (MM processing is emerging as an innovative and highly effective material processing method offering many advantages over conventional methods especially for sintering application. In the present study, using a mixed powder of the Ni55Nb25Ti15Pt5 metallic glassy powder prepared by an argon gas atomization process blended with 50 vol.% Sn powder, the MW-induced heating and sintering were carried out by a single-mode 2.45 GHz MW applicator in a magnetic field maximum. The structure and thermal stability of the sintered glassy composite specimens were investigated. The addition of Sn particles enhanced densification of the sintered Ni-based metallic glassy alloy powders.

We developed new Ti-based bulk metallic glassy (BMG) alloys in Ti-Zr-Pd-Cu-Sn system without Ni element for application as biomaterials. These BMG alloys have a high potential to be applied as metallic biomaterials in various forms, such as melt-spun ribbons and cylindrical rods with a diameter of 4 mm. We also investigated of new Ti-based BMG alloys with higher glass-forming ability (GFA) for medical market as dental implants. These Ti-based BMG alloys do not contain Ni, Al and Be elements which are well known to be harmful for human body. In particular, a rod sample of the Ti(44.1)Zr(9.8)Pd(9.8)Cu(30.38)Sn(3.92)Nb(2) BIVIG alloy with a diameter of 3 mm produced by copper mold casting exhibits a compressive strength of 1990 MPa and a Young&apos;s modulus of 99 GPa. In addition, the Ti(44.1)Zr(9.8)Pd(9.8)Cu(30.38)Sn(3.92)Nb(2) BMG shows a large supercooled liquid region of 62 K and a reduced glass-transition temperature, T(rg)(=T(g)/T(m)) of 0.61. The high thermal stability of the supercooled liquid allowed the fabrication of cylindrical rod specimens up to 5 mm in diameter. Thus the studied alloy exhibits high glass-forming ability (GFA) and a large size enough to be used for dental implants. The Ti(44.1)Zr(9.8)Pd(9.8)Cu(30.38)Sn(3.92)Nb(2) BIVIG alloy also has a high corrosion resistance and is passivated at the lower passive current density of approximately 10(-2) A m(-2), 10(-3) A m(-2) and 10(-2) A m(-2), in 1 mass% lactic acid, PBS (phosphate-buffered saline without calcium and magnesium salts solution) and HBSS (Hank&apos;s balance salt solution without calcium, magnesium and phenol red), respectively, at 310 K, which are lower than those of pure Titanium and Ti-6Al-4V alloy. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.

In the present study, we prepared Ni-59.35 Nb-34.45 Sn-6.2 metallic glassy alloy powder by an argon gas atomization process. Microwave (MW)-induced heating and sintering was carried out by a single-mode 2.45 GHz MW applicator in the separated magnetic field or electric field using the obtained glassy powders. The structure and thermal stability of the sintered glassy alloy specimens were investigated.

Metallic glasses exhibit low viscosity in a temperature range between the glass transition and the crystallization temperature, a feature that allows successful sintering of glassy powders. Microwave heating, being volumetric, has significant advantages over conventional heating in materials processing, such as substantial energy savings, high heating rates and process cleanliness. In the present study, we investigate the stability of Cu50Zr45Al5 glassy powders and the formation of a bulk two-component metallic glassy-crystal sample by microwave heating in a single-mode cavity (915 MHz) in an alternating magnetic field.

We summarize the structural features of several Cu-based alloys known so far having high glass-forming ability and investigate the influence of Ag addition on their crystallization behavior. According to synchrotron-beam X-ray radiation studies, an oC68 Cu10Zr7 phase is found to be a good approximant to the Cu-Zr-Ti and Cu-Zr-Ag glassy phases. The structure of the bulk glassy Cu36Zr48Al8Ag8 and Cu44Ag15Zr36Ti5 alloy samples studied by high-resolution TEM was found to contain well developed medium-range order zones and nanoparticles, respectively. An influence of the cooling rate on the structure and properties of the Cu-based glassy alloys on heating was also studied. The crystallization kinetics of Cu55Zr45, Cu50Zr50, Cu55-xZr45Agx (x = 0, 10, 20), Cu44Ag15Zr36Ti5, Cu45Zr45Al5Ag5 and Cu36Zr48Al8Ag8 glassy alloys was also analyzed substantially. Cu35Zr45Ag20 alloy was found to exhibit possible phase separation upon heating within a supercooled liquid region.

Glass formation by mechanical milling was achieved in a multicomponent Ni-based alloy system. It was found that the milling time required for forming a fully glassy phase decreased with the increase in Zr content. The enhanced atomic size mismatch of constituents was responsible for the increase of glass forming ability of these alloys. The transformation from crystalline to glassy phase might be due to the destabilization of crystalline phase, induced by a combination of factors involving refinement of grain size, high pressure exerted to powders during repeated collision, and elastic mismatch energy.

In the present study we investigate the stability of Cu50Zr45Al5 and Ni59Ti16Zr20Sn5 glassy powders and the formation of the bulk metallic glassy samples by microwave heating in a single mode cavity (915 MHz) in the alternating magnetic field maximum. Metallic glasses exhibit low viscosity at temperatures close to the glass-transition which allows for the processing of glassy powders. Microwave heating being a volumetric heating has significant advantages over conventional heating in materials processing, such as substantial energy savings, high heating rates and process cleanness.

We present a Ni-based crystal-glassy composite material having superior strength paired with a considerable ductility of 15%. The formation of a metastable crystalline phase in a glassy matrix during solidification has been proven capable of promoting a strain-induced martensitic transformation leading to enhanced plasticity under compression at room temperature. Underlying mechanisms of plastic deformation are discussed in terms of the interplay between dislocation slip in the crystalline phase and shear deformation in the glassy matrix. We suppose that the strain-induced martensitic inclusions serve as strong barriers for shear band propagation, promoting shear band branching and multiple shear band formation, thus extending the ductility and preventing a premature brittle fracture. The acoustic emission technique has been employed to clarify the kinetics of transformation and stages of plastic deformation.

Microwave (MW) heating and sintering of Ni-based bulk metallic glass matrix composite, consisting of gas-atomized Ni52.5Zr15Nb10Ti15Pt7.5 glassy alloy and tin powders, was performed without external pressure by using a single-mode applicator. These powders could be heated well in the magnetic field maximum, but not heated enough in the electric field maximum. A bulk sintered body with the retention of the amorphous phase was obtained below 783 K in an inert atmosphere. The addition of Sn particles promoted the densification of the sintered Ni52.5Zr15Nb10Ti15Pt7.5 glassy specimen. The results suggest that the MW sintering of metallic glasses offers a flexibility of fabricating bulk metallic glasses and metallic glass matrix composites. [doi: 10.2320/matertrans.MRA2008603]

It is known that bulk metallic samples reflect microwaves while powdered samples can absorb such radiation and be heated efficiently. In the present work we studied heating mechanisms of metallic powders in a multimode 2.45 GHz microwave applicator. The present paper shows direct evidence of penetration of a layer of metallic powder by microwave radiation and provides theoretical explanation of such behavior. The most effectively heated powder is Fe because both eddy current loss (in alternating H-field) and magnetic reversal loss (in alternating E-field) mechanisms act in case of such metal. Diamagnetic metals Sn and Cu are heated better than paramagnetic Ti while Au is also only slightly heated. Cu- and Ni-based metallic glassy powders are also moderately heated. Weak heating of Au powder (which is a noble metal) can be explained by the absence on the particles of the oxide layer (shell), which allows eddy currents flowing through larger area compared to other metals, and reflection mechanism works much better in such case. (c) 2008 American Institute of Physics. [DOI: 10.1063/1.3009677]

High-strength Ti-Fe-Cu, Ti-Fe-Cu-Nd, Ti-Fe-Cu-Sn and Ti-Fe-Cu-Nd-Sn alloys were produced in the shape of arc-melted ingots with the dimensions of about 30 mm in diameter and 10 mm in height. The structure of these alloys consists of an ordered cP2 Ti(Fe,Cu) intermetallic compound and a disordered BCC c12 beta-Ti solid solution. The high strength values result from the high Fe and Cu contents in the supersaturated beta-Ti solid solution (solution hardening) and high hardness of the Ti(Fe,Cu) intermetallic compound having a rounded morphology. The high strength and ductility values can be achieved without using the injection mould casting or rapid solidification procedure. Fine structure of the studied alloys, their deformation behavior and the fractography are also studied. (C) 2008 Elsevier B.V. All rights reserved.

Vitrification of metals and alloys has received much attention in the field of materials science. Although some progress has been made, this phenomenon has yet to be fully understood. Herein, we investigate the vitrification process of pure Ni using an ab initio molecular dynamics simulation. The results of the molecular dynamics simulation and predictions from the specific volume and density diagrams as well as a casting experiment indicate that Ni may have a high reduced glass transition temperature but due to kinetic reasons is not a good glass former. The results of the present work provide new information about the glass-transition phenomenon and suggest that the reduced glass transition temperature is only an indicator of how easily can glass be formed and that its stability is a significantly more important feature.

As it is known from the experiment that bulk metallic samples reflect microwaves while powdered samples can absorb such a radiation and be heated efficiently. In the present paper we investigate theoretically the mechanisms of penetration of a layer of metallic powder by microwave radiation and microwave heating of such a system. (C) 2008 Elsevier B.V. All rights reserved.

Structural features of a glassy Cu60Zr30Ti10 alloy are studied by using the real-space pair distribution and radial distribution functions. The experimental X-ray diffraction data obtained in a synchrotron beam were used to derive radial distribution function through Fourier transformation processing. Based on these and the results of transmission electron microscopy observation it is suggested that a certain degree of medium-range order in this alloy maintains up to about 2 nm distance. It is also shown that the interatomic distances closely correspond to those of oC68 Cu10Zr7 compound which allows obtaining high relative density of the glassy alloy. The formation of icosahedral local order is also presumed. (C) 2007 Elsevier B.V. All rights reserved.

In this work, we study the cooling behavior of several typical bulk glassy alloys on casing and present the relationship between the thermal conductivity of a glassy alloy and the cooling rate upon mold casting. The cooling rates obtained for Ti-, Zr-, Pd-, and Cu-based bulk glass forming alloys are found to scale with the thermal conductivities of the studied glassy alloys.

The plastic deformation and compression fracture of cylindrical samples of the bulk metallic glass Zr64.13Cu15.75Ni10.12Al10 have been studied in the temperature range 300-4.2 K. The deformation curve at 300 K is serrated due to the propagation of narrow shear bands. Catastrophic, uncontrollable fracture of samples, occurring as a result of the propagation of a macroscopic shear band with speed (of the order of 10(3) m/s) comparable to the Sound speed, is observed at deformation similar to 3-4%. When the temperature is lowered from 300 to 170 and 77 K the deformation changes from serrated to smooth. An interesting low-temperature anomaly of the deformation process is found: "slow" (with speed of the order of 10(-6) m/s) propagation of a single macroscopic shear band is observed at 170 and 77 K. When the samples are cooled to 4.2 K their macroscopic plasticity vanishes, and they undergo fracture, just as at 300 K, as a result. of the propagation of a catastrophic shear band with near-sound speed. (c) 2008 American Institute of Physics.

The purpose of the current paper is to study the influence of Ti, V, Nb, Al, Sn and Pd additions on the glass-forming ability, formation of a supercooled liquid region and a devitrification process of some Ni-Zr glassy alloys as well as to compare the results with those obtained for similar Cu-based alloys studied earlier. The Ni-based glassy alloys were investigated by using X-ray diffraction, differential scanning and isothermal calorimetries. Although the studied Ni-based alloys showed high values of the reduced glass-transition temperature of about 0.6, their glass-forming ability is quite low. This fact may be explained by low stability of the supercooled liquid against crystallization and formation of the equilibrium intermetallic compounds with a high growth rate compared to those observed in similar Cu-based alloys studied earlier. Relatively low thermal conductivity of Ni-based alloys is also found to be another factor limiting their glass-forming ability. (C) 2007 Elsevier B.V. All rights reserved.

New Ni-Zr-Cu-Ti-Al bulk metallic glasses (BMGs) were fabricated on the basis of ternary Ni-Zr-Al alloys. The addition of Cu and Ti increased the glass-forming ability (GFA) of Ni-Zr-Al alloys. These BMGs exhibited high thermal stability and relatively large supercooled-liquid region. With the substitution of Ni by Cu from 0 to 19.2 at%, the GFA of Ni-Zr-Ti-Al alloys was enhanced and its glass transition temperature T-g, onset crystallization temperature T-x, and onset melting temperature T-m all decreased. When Cu content was 24 at%, the GFA decreased again. The BMG rod with a maximum diameter of 2 mm was fabricated in the Ni43.7Zr19.2Cu19.2Ti13.9Al4 alloy and the compression tests indicated that it had high fracture strength of about 2400 MPa, Young's modulus of 121 GPa, elastic strain of 0.02 and plastic strain of 0.009 at ambient temperature.

Ni-based bulk glassy alloy composites (GACs) simultaneously with ultrahigh strength and enhanced ductility and satisfying large-size requirements were fabricated by spark plasma sintering of gas-atomized Ni(52.5)Nb(10)Zr(15)Ti(15)Pt(7.5) glassy alloy powder blend with ceramic or metal powders. No crystallization of metallic glassy matrix and good bonding state between the particles are responsible for good mechanical properties of the fabricated bulk GACs. The improvement of plastic ductility of the fabricated bulk GACs originates from the structural inhomogeneity caused by the particles inclusion. The additional particulates act as a resisting media causing deviation, branching, and multiplication of shear bands. (c) 2008 American Institute of Physics.

The influence of the cooling rate on the structure, microhardness, relaxation, and devitrification behavior of Cu44Ag15Zr36Ti5 glassy alloy on heating is studied in the present work. According to transmission electron microscopy investigations, the structures of Cu44Ag15Zr36Ti5 glassy ribbon and bulk samples are somewhat different. The structure of the ribbon samples is amorphous while, the nanoscale clusters of the crystalline phase (highly ordered regions) are formed in the bulk samples. It is reflected in the shift of the x-ray diffraction peak, in the magnitude of the heat of structure relaxation and crystallization, as well as in the change in the Vickers microhardness. An analysis of the cooling curve is also performed.

Nanostructured and x-ray-amorphous films in the TiB(2)-B(4)C system are prepared by nonreactive magnetron sputtering in the absence and presence of an additional external magnetic field with inductions of up to 0.3 T. The properties of the deposited films, such as the grain size, phase composition, dominant texture, roughness, and hardness, are investigated using transmission electron microscopy, microdiffraction, x-ray powder diffraction. atomic force microscopy, and microdurometry. The specific features of the phase diagram as applied to films and the effect of application of the magnetic field on their properties are discussed.

Although, bulk metallic glasses exhibit remarkable mechanical, physical and chemical properties, their critical size (the largest size of fully glassy sample produced by casting) is limited. The utilization of a welding technique enables producing larger glassy samples. Ni53Nb20Ti10Zr8CO6Cu3 glassy alloy ribbon samples prepared by melt spinning of the pre-alloyed arc-melted ingots were welded by the electron-beam and fiber laser-beam welding techniques. The detailed structural investigations of the welded bead and thermally affected zone were performed by micro-area X-ray diffractometry, scanning and transmission electron microscopy. At certain optimized welding conditions the amorphous structure can be retained after melting. The obtained data are promising for future applications of the laser and electron-beam welding techniques to glassy alloys. (C) 2007 Elsevier B.V. All rights reserved.

We fabricated Zr55Cu3OAl10Ni5 bulk metallic glassy matrix composites (MGMCs) containing ceramic Al2O3 or Si3N4 particulates by a spark plasma sintering (SPS) process. Microstructure, thermal stability and mechanical properties of the fabricated bulk MGMCs were investigated. The matrix of the fabricated MGMC specimens maintained a glassy phase after the SPS process. The fabricated MGMC specimens showed thermal stability similar to that of the original gas-atomized glassy alloy powder. Good bonding between the metallic glassy powder and ceramic particulate was recognized. The added ceramic Al2O3 or Si3N4 particulates were found to be homogenously distributed within the sintered samples and play an important role in the enhancement of plasticity. (C) 2007 Elsevier B.V. All rights reserved.

We have fabricated Zr(55)Cu(30)Al(10)Ni(5) metallic glassy matrix composite by a spark plasma sintering process using a mixed. powder of gas-atomized Zr(55)Cu(30)Al(10)Ni(5) glassy alloy powders blended with 10 vol.% ZrO(2) powders. The structure, thermal stability, and mechanical properties of the sintered bulk glassy matrix composite were investigated. The ZrO(2) particles were homogeneously dispersed in the Zr(55)Cu(30)Al(10)Ni(5) glassy matrix. No crystallization of the glassy matrix occurred during the spark plasma sintering process. The crystallization behavior of the sintered. glassy matrix composite was similar to that of the glassy alloy powder. The plastic ductility of the sintered Zr(55)Cu(30)Al(10)Ni(5) glassy matrix composite was enhanced by adding the ZrO(2) particulates into the metallic glassy alloy. The improvement was originated from the structural inhomogeneity caused by the microparticles inclusion.

This article summarizes the general structural features and important properties of quasicrystals, a relatively new class of materials belonging to solid-state substances. Quasicrystals, which have a long-range quasiperiodic order but no three-dimensional translational periodicity, are structurally different from both conventional crystals and glassy solids. Although applications are still highly limited, quasicrystals are attracting significant attention as a structural constituent of mixed-phase materials exhibiting high strength together with certain ductility and can be applied as structural materials.

The deformation behaviour of Zr60Cu16Ni14Al10 glassy alloy was found to exhibit cleavage-like fracture relief paired with typical vein patterns. The mirror-like cleavage area fraction is found to be comparable with that of vein areas. These two types of patterns alternate on the fracture surface in a direction normal to shear deformation. The structure of the studied alloy was characterised by X-ray diffractometry and scanning and transmission electron microscopy. A small volume fraction of crystals in the form of eutectic colonies were found here and there in the specimen. No distinct difference in the glassy structure of the cleavage-like fracture areas and the areas corresponding to vein patterns was found within the resolution of experimental techniques employed.

For future extension of application fields for bulk glassy alloys, it is important to develop a new type of glassy alloys which exhibit simultaneously high strength, low Young's modulus, large elastic elongation, high ductility, high corrosion resistance, low density, high specific surface area, etc. Considering that bulk glassy alloys in non-ferrous metal base systems possess unique characteristics of high strength, low Young's modulus, large elastic elongation, high fracture toughness and high corrosion resistance, they are expected to become an important candidate material for structural applications. One of the ways to develop a new material with the above-described properties is to fabricate ductile bulk glassy alloys containing open or closed pores in a wide range of volume fraction. Mechanical properties of closed-pore type porous bulk glassy alloys are presented. Moreover, in the present work, we review our recent work on the porous glassy Pd42.5Cu30Ni7.5P20 alloys and present an analysis of stress concentration around spherical pores. © 2007 Elsevier B.V. All rights reserved.

Zr-based metallic glass nanowires and nanoparticles were produced in melt-spun Zr-(Ce, Pr, Nd)-Al-Ni alloys by using the liquid-state immiscibility of Zr and a rare-earth element. In the equiatomic Zr and rare-earth alloy, an interconnected two-phase structure is formed, probably by spinodal decomposition. The interconnected structure was directionally elongated at the edges of the ribbon where the melt was heavily deformed by melt-spinning. In the rare-earth-rich alloy, fine isolated Zr-rich spheres precipitated in the rare-earth-rich matrix by the nucleation and growth process. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

We report that an approximant phase was initially obtained in amorphous Ti40Zr20Hf20Pd20 alloy. In the initial stage of the devitrification process, the approximant phase transforms into an icosahedral (1) phase with a high thermal stability while the cF96 Zr2Ni-type (space group Fd (3) over barm with a = 1.25 nm and 96 atoms cell(-1)) particles precipitate from the amorphous matrix. Eventually the I phase grows to several hundred nanometers when annealed at about 1000 K and then transforms into the Zr2Ni-type phase with an endothermic reaction. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The structure of the high strength and ductile Ti60Fe20Co20 alloy in its as-solidified state consists of the primary dendrites of cP2 Ti(Fe,Co) compound and an eutectic consisting of the cP2 Ti(Fe,Co) compound and BCC cI2 beta-Ti solid solution. The cI2 beta-Ti solid solution phase exhibits a dislocation-type deformation mechanism, while no dislocations but shear bands were found in the cP2 Ti(Fe,Co) phase. Strain-induced amorphization is observed in cooperation with the formation of the martensitic mP4 phase from the crystalline cP2 intermetallic compound. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effect of electron irradiation on stability of nanocrystallites dispersed in a glassy matrix of a Cu50Zr45Ti5 bulk metallic glass (BMG) alloy was investigated. Microstructural evolution during electron irradiation was observed and analyzed by means of conventional and high-resolution transmission electron microscopy (CTEM and HRTEM) and X-ray energy dispersive spectroscopy (EDS). The crystalline nanoparticles of monoclinic CuZr phase formed in-situ in as-cast Cu50Zr45Ti5 alloy exhibited a high stability against electron irradiation. No obvious changes in their size, morphology, and crystal structure were observed during electron irradiation, though new crystalline nanoparticles nucleated and precipitated in the glassy matrix under electron irradiation. The new nanoparticles formed upon irradiation have a similar composition and crystal structure to those formed in-situ in the as-cast alloy. The nanocrystalline precipitates in the glassy matrix are proposed to be mainly due to electron knock-on effect under electron irradiation, which promotes atomic diffusion and assists the crystallization of the glassy phase. The present result indicates that electron irradiation to metallic glasses has potential for producing nanocrystalline structure and nanocrystalline-glassy composite structure.

This paper presents an influence of Ag addition on the glass-forming ability and devitrification behavior of Cu-Zr glassy alloys on heating. The crystallization kinetics and structure changes in Cu45Zr45Ag10 and Cu35Zr45Ag20 glassy alloys on heating were studied by X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. Based on the results obtained one can assume that the improvement of the glass-forming ability of the Cu-Zr alloys by the addition of Ag is connected with a particular crystallization mechanism and a higher reduced glass-transition temperature of the Cu45Zr45Ag10 ternary alloy compared to the binary Cu55Zr45 counterpart. As observed in the present work crystallization of the Cu-Zr-Ag alloys is found to cause embitterment of the samples and should be avoided as these alloys are considered to be used as structural materials. The Cu35Zr45Ag20 alloy shows possible submicron-scale phase separation upon annealing. (C) 2007 Elsevier B.V. All rights reserved.

This paper presents an influence of Al and Ag additions on the thermal stability and devitrification behavior of Cu-Zr glassy alloy on heating. The crystallization kinetics and structure changes in Cu50Zr45Al5 and Cu45Zr45Al5Ag5 glassy alloys on heating were studied by X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. The addition of Al and Ag to Cu50Zr50 alloy drastically changes its crystallization behavior. It is found that Cu50Zr45Al5 and Cu45Zr45Al5Ag5 glassy alloys show rather eutectic crystallization forming mostly stable phases while Cu50Zr50 glassy alloy exhibits a primary crystallization behavior forming a metastable monoclinic CuZr phase at the initial crystallization stage.

A Ni50Pd30P20 bulk glassy alloy contains nanoscale clusters/medium-range order (MRO) zones. However, as this alloy exhibits "nucleation and growth" type transformation on heating, these nanoscale clusters are believed to have an under-critical size. The relatively large activation energy is the reason why these nanoscale clusters do not grow significantly upon deformation. A clear nucleation and growth of a Ni2Pd2P phase is observed near the micro-crack area. The existence of MRO zones as structural inhomogeneities and blockage of the crack-tip propagation area by the dynamically formed nanoparticles may lead to stabilization of deformation. (C) 2006 Elsevier B.V. All rights reserved.

Thick film magnets (similar to 3.2 mu m) deposited on silicon substrate at processing temperatures lower than 400 degrees C, exhibiting high coercivity (H-c similar to 604 kA m(-1)). high maximum energy product [(BH)(max) = 95 kJ m(-3)] and good surface properties, were obtained by sputtering technique. The effects of sputtering power, substrate temperature (T-s) and film thickness on the magnetic properties of the films were studied. Films exhibiting very good hard magnetic properties are mainly made up of nanosized hard (L1(0)-FePt) and soft (Fe2B and Fe3B) magnetic phases.. which are exchange coupled. The exchange spring behavior in these films was investigated and a high recoil rate of more than 90% was obtained. The ability to deposit permanent magnet thick films exhibiting good hard magnetic as well as surface properties on silicon. as demonstrated in the present work, is very promising for the fabrication of micromagnets for magnetic MEMS. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ni-free Ti-based bulk metallic glass (BMG) alloys were reported to have a high enough glass forming ability (GFA). In this study, the glass forming ability of Ti-based BMG alloys without Ni and Be additions is analyzed using Inoue's empirical rules, bonding order (B-o), and molecular d-orbital energy values (M-d). The developed Ti-based BMG alloys revealed a separable location on the (B-o) over bar-(M-d) over bar diagram which presents the direction for design of Ti-based BMG alloys with high GFA. (c) 2007 American Institute of Physics.

Ni-based bulk metallic glasses (BMGs) with a large size were fabricated by spark plasma sintering (SPS) of a gas-atomized Ni52.5Nb10Zr15Ti15Pt7.5 glassy alloy powder. The structure and thermal stability of the sintered specimens as well as the interface characteristics between powder particles were investigated. The sintered glassy specimens with nearly 100% relative density were obtained by the SPS process at a sintering temperature of 773 K with a loading pressure of 600 MPa. It was achieved using relatively low sintering temperature, short holding time, and rapid cooling during the SPS process. The results suggest that the BMGs fabricated by the SPS process opens possibilities of application as structural materials offering excellent properties and satisfying large-size requirements. (c) 2007 American Institute of Physics.

A new Ti-based bulk-metallic glassy (BMG) alloy without Ni was developed in various forms such as melt-spun ribbon and cylindrical rods. Ti metal and Ti-based alloys are well known as biomaterials because Ti has good biocompatibility with the human body. We examined mechanical and chemical properties of a newly developed Ti-based BMG alloy in comparison with pure Ti metal and Ti-6Al-4V alloy, which are used for biornaterials. The new Ti-based BMG (Ti45Zr10Pd10CU31Sn4) alloy does not contain Ni, Al, and Be elements, which are known to be toxic. The Ti45Zr10Pd10CU31Sn4 BMG alloy rod with a diameter of 3 mm, which is produced by copper mold casting, exhibits a compressive strength of 1970 MPa and a Young's modulus of 95 GPa. In addition, the Ti45Zr10Pd10CU31Sn4, BMG alloy shows a supercooled liquid region of 56 K and a reduced glass-transition temperature, T-rg (=T-g/T-1), of 0.56. The high thermal stability of supercooled liquid has enabled the fabrication of a cylindrical rod specimen with a diameter of 4 mm. This alloy exhibits precipitation of a primary nanoscale icosahedral phase upon devitrification followed by the formation of a metastable unidentified phase. Ti2Cu and Ti3Sn are stable phases formed in this alloy. The Ti45Zr10Pd10Cu31Sn4 BMG alloy has a high corrosion resistance and is passivated at a lower passive current density of approximately 10(-2) A/m(2) compared to those of pure titanium and the Ti-6Al-4V alloy in 1 mass% lactic acid and phosphate-buffered saline solutions at 310 K.

If a metal contracts upon solidification, the specific volume of a metallic liquid phase must not be smaller than that of the corresponding crystal. As molten metals have higher thermal expansion coefficients compared with those of the corresponding crystals, the intersection point of two specific-volume-temperature plots of the liquid and the corresponding solid crystalline phase by analogy with Kauzmann's paradox for entropy could be treated as an ideal glass-transition temperature. This paper describes this phenomenon observed for a number of pure metals and gives a semiempirical criterion for the achievement of a good glass-forming ability. © 2007 Materials Research Society.

The formation of a supercooled liquid region and devitrification behaviour of metallic glasses on beating are discussed in relation with the glass-transition phenomenon observed using differential scanning and isothermal calorimetries as well as X-ray diffraction and transmission electron microscopy (TEM). One of the most clear sequences of the glassy paired left right arrows supercooled liquid phase transition is the change of the devitrification behaviour and the kinetics of the devitrification reaction in Al-based and some other alloys after the transition from the glassy to the supercooled liquid state. The significant variation in the devitrification behaviour and thermodynamic parameters indicate the difference between the glassy and the supercooled liquid phases. (C) 2006 Elsevier B.V. All rights reserved.

The high strength metastable Ti-Fe-Co alloys were produced by arc-melting in the shape of distorted semi-spherical ingots with the dimensions of about 25-30 mm in diameter and 7-10 mm in height. The structure of the hypereutectic Ti-Fe-Co alloys (at Fe/Co ratio &gt;= 1) studied by X-ray diffractometry and scanning electron microscopy consisted of the primary dendrites of an ordered cP2 Ti(Fe, Co) compound and an eutectic consisting of the cP2 Ti(Fe, Co) compound and a disordered BCC cI2 beta-Ti solid solution. The strongest Ti-Fe-Co alloys have a hypereutectic structure and exhibit a high strength exceeding 2000 MPa and a plastic deformation of about 15%. The quaternary Ti67Fe14Co14Sn5 alloy exhibits a high strength of 1830 MPa and the largest plastic strain of 24%. The deformation behavior and the fractography of Ti-Fe-Co and Ti-Fe-Co-Sn alloys are studied in detail. The formation of a composite-like structure with hard carcass of the intermetallic phase in the relatively soft eutectic matrix enabled both high strength and ductility. The accommodation deformation can be explained by the intergranular sliding of the primary Ti(Fe, Co) dendrites in the softer eutectic matrix. Rough primary dendrites and eutectic rods of the cP2 intermetallic phase act as efficient barriers for shear strain and cracks propagation, while fine eutectic rods of submicron size are quite effortlessly cut by deformation bands and cracks. It is shown that the high strength and ductility values for Ti-based alloys can be achieved without using the injection mould casting or rapid solidification procedure. (C) 2006 Elsevier B.V. All rights reserved.

The variation of free volume and elastic properties of the Cu55Zr30Ti10Pd5 glassy alloy on heating was studied. The structure changes on heating were studied by synchrotron X-ray diffraction, differential scanning and isothermal calorimetries. The studied glassy alloy shows a rather high Poisson's ratio exceeding 0.42 which is maintained after the structure relaxation and primary devitrification. Young's and Shear modules decrease upon primary devitrification while Bulk modulus exhibits a maximum after structural relaxation. (c) 2006 Elsevier B.V. All rights reserved.

Metallic glasses as non-equilibrium materials crystallize at a critical temperature, accompanying their embrittlement. The size of glassy alloys is dependent on their glass-forming ability. The development of an appropriate Joining technique is important for the extension of industrial applications. In the present study, we examine crystallization behavior of Zr55Al5Ni5Cu30 glassy alloy upon annealing. In the beginning of the crystallization process, a clustering, a crystal nucleation and the crystal growth processes take place sequentially. The phase transition behavior was examined by differential scanning calorimetry (DSC). The kinetics of the crystallization process can be analyzed by the changes in the volume fraction of the crystalline phase which scales with the exothermic heat release and density measurement. The crystallization process in the Zr55Al10Ni5Cu30 alloy is found to be diffusion-control led. The values of the Avrami exponent are between 2.3 and 2.8. Therefore, the velocity of nucleation and crystallization processes should scale with the diffusion velocity of the constituent elements in the metallic glass. The diffusion rate can be estimated using the diffusion coefficients of the constituent elements, as a function of time and temperature. The slope of the calculated iso-precipitation line of CuZr2 phase on the fixed TTT diagram is well fitted with the lines representing ductile and brittle behavior of the sample. The results indicate that the most harmful crystalline phase, which causes embrittlement is CuZr2. The influence of Si contamination on the crystallization behavior is also studied in the present work.

This article presents a comparative study of the deformation-induced structural changes observed within a glassy phase in two different Zr- and Ni-based alloys. Ductile Zr65Al7.5Ni10Pd17.5 bulk glassy alloy, which exhibits dynamic nanocrystallization forming a crystalline cubic phase within shear bands on plastic deformation, is presumed to contain pre-existing nuclei. On the contrary, no obvious dynamic nanocrystallization is observed within the shear bands in the glassy phase of the Ni50Pd30P20 bulk alloy, which, however, contains clear medium-range order zones on the order of 1 nm in size in an as-solidified state. This alloy exhibits nucleation and growth-transformation behavior on heating. At the same time, clear nucleation and growth of the cubic Ni-based phase are observed near the microcrack area in the deformed sample. High energy released at the time of the microcrack propagation caused nanocrystallization and blockage of the crack-tip propagation.

Glass-formation and devitrification of the glassy phase in the Ni-Nb-Zr-Ti and Ni-Nb-Zr-Ti-NM (NM, noble metals) system alloys exhibiting the supercooled liquid on heating were investigated. The crystallized structure and kinetics of devitrification of Ni-Nb-Zr-Ti-Pd glassy alloy are studied in detail. The formation of the glassy single phase has been proven using high-resolution transmission electron microscopy (TEM). The addition of Zr and Pd increases the supercooled liquid region of the Ni60Nb25Ti15 (numbers indicate at.%) alloy from 44 K to about 50 K. The cP2 TiNi phase was found to form during the first exothermic phase transformation in all studied alloys. The addition of Zr to Ni-Nb-Ti alloy prevents formation of oP8 Ni3Nb phase observed in the Ni60Nb25Ti15 alloy and initiates formation of the primary Ni10Zr7 phase while the additions of both NM and Zr effectively refine cP2 TiNi particles size. Definite fractions of rhombohedral R and hR14 Ni4Ti3 phases were also observed in NM-bearing alloys. Significantly lower growth rates of the devitrification products in the NM-bearing alloys compared to the Ni-Nb-Ti one may be the reason for the improvement of glass-forming ability (GFA). (c) 2006 Elsevier B.V. All rights reserved.

Rapidly solidified Al-Y-Ni-Co-Pd alloys contain highly dispersed primary alpha-Al nanoparticles of about 5 urn in size homogeneously embedded in the glassy matrix with an extremely high density of precipitates of the order of 10(24) m(-3). These particles grow at the temperature below a glass-transition temperature. The first direct observation of micro-strain regions and dislocations quenched in nanoparticles with a size about 5 nm is provided. (c) 2006 Elsevier B.V. All rights reserved.

This letter presents microwave sintering of Ni52.5Zr15Nb10Ti15Pt7.5 glassy alloy powder. It was observed that the alloy was heated well in the magnetic field maximum, while it was not heated enough in the electric field maximum. A sintered sample with a glassy structure was obtained at 843 K in an inert atmosphere (Ar).

Using ultrasonics, acoustic attenuation characteristics of Pd40Cu30P20Ni10, Zr65Pd12.5Ni10Al7.5Cu5, Cu55Zr30Ti10Pd5, and Ti41.5Cu47.5Ni7.5Hf5Zr2.5Sn1 glassy alloys were examined in comparison with crystalline metals based on complex viscoelasticity. The glassy alloys favor to absorb the longitudinal one, but crystalline materials absorb the shear one, associated with periodicity and randomness of energy potentials, respectively. In sharp contrast to crystalline materials, Nyquist [Bell Syst. Tech. J. 11, 126 (1932)] diagrams of the glassy alloys are characterized by large areas of the third and the fourth quadrant in the loop, suggesting advancement of the relay in phase, that is, increment of the imaginary parts in complex waves. (c) 2007 American Institute of Physics.

Elastic properties, phase composition, microstructure and specific volume changes in the Zr65Ni10Cu5Al7.5 Pd-12.5 glassy alloy during progressive devitrification have been studied by ultrasonic pulse, X-ray diffractometry, transmission electron microscopy and Archimedean methods, respectively, in terms of structure and properties change. On heating the glassy alloy initially forms an icosahedral phase and then a mixture of tI12 Zr2Niss and beta-Zr-ss crystalline phases after annealing at 993 K for 300 s, and lastly tI12 Zr2Nss, tI6 Zr2Pd and hP9 Zr6Al2Ni crystalline phases after prolonged annealing at 993 K for 7.2 ks. In an as-solidified state the alloy shows high Poisson's and K/G ratios of 0.42 and 7, respectively. These parameters are responsible for its good ductility. The structural changes are accompanied by decreases in specific volume, bulk modulus, Lame parameter and Poisson's ratio. Small specific volume changes upon primary devitrification suggest a close relation between the glassy and the icosahedral structures. The existence of the icosahedral local order, which exhibits rigidity for three-dimensional shear deformation with mixed mode 11 mode 111, may be responsible for good elasticity of the glassy alloy. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Using a mixed powder of argon gas-atomized Zr55Cu30Al10Ni5 metallic glassy alloy powder blended with 10 vol% ZrO2, powder, Zr55Cu30Al10Ni5 bulk metallic glassy matrix composite was fabricated by a spark plasma sintering process. The structure, thermal stability and mechanical properties of the sintered bulk metallic glassy matrix composite were investigated. The ZrO2, particles were homogeneously dispersed in the Zr55Cu30Al10Ni5 glassymatrix. No crystallization of the glassy matrix occurred during the spark plasma sintering process. The crystallization behavior of the sintered composite was similar to that of the metallic glassy powder. The sintered composite specimen exhibited larger plastic ductility than that of the as-cast Zr55Cu30Al10Ni5 glassy alloy rod specimen. The increase in the plastic ductility is proposed to originate from the structural inhomogeneity caused by the ZrO2, ceramic particles.

The high strength metastable Ti-Fe-Co alloys were produced by arc-melting in the shape of nearly semi-spherical ingots. The structure of the hypereutectic Ti-Fe-Co alloys (with equiatomic Fe and Co contents) is found to consist of the primary dendrites of an ordered cP2 Ti(Fe,Co) compound and an eutectic consisting of the cP2 Ti(Fe,Co) compound and a disordered BCC c/2 P-Ti solid solution. Hypereutectic Ti-Fe-Co alloys exhibit a high mechanical strength exceeding 2000 MPa and a plastic deformation of 16%. The deformation behavior and the fractography of Ti-Fe-Co alloys are studied in detail. The beta-Ti solid Solution phase exhibits a dislocation-type deformation mechanism, while no dislocations but only shear bands were found in the cP2 IM Ti(Fe,Co) phase. This phase deforms by localized shear deformation and also undergoes accommodation deformation likely by intergranular sliding. The formation of partially ordered structure may enhance plasticity of Ti-Fe-Co compared to Ti-Fe alloys. Moreover a good crystal lattice correspondence between cP2 and cI2 phases was found. Rough primary dendrites and eutectic rods of the cP2 intermetallic phase act as efficient barriers for shear strain and crack propagation. (c) 2006 Elsevier Ltd. All rights reserved.

Using ultrasonics, acoustic characteristics of Pd40Cu30P20,. Zr55Cu30Al10Ni5, Zr65Pd12.5Ni10Al7.5 Cu-5, Cu55Zr30Ti10Pd5, Cu45Zr20Hf25Ag10 and Ti41.5Cu42.5Ni7.5Hf5Zr2.5Sn1 glassy alloys were examined in terms of complex elasticity. The order of bulk modulus (K), Lame parameter (A), Young (lambda) and shear (G) moduli of the glassy alloys is monopoltical character of glassy alloys, except for polymers and rubbers. For metals and alloys, ceramics, polymers and glassy alloys, Poison's ratio correlates well to ratio G/K Complex elasticity indicates that viscoelasticity of the glassy alloys is predominated by volumetric motion.

This paper describes the relation between the change in the position of the first X-ray diffraction maximum in reciprocal space and the first maximum of the distribution function in real space for the Ge50Al40Cr10 amorphous alloy. It is also shown that the first diffraction maximum of the interference function carries the most significant information about the interatomic distances in real space while the subsequent peaks of the interference function are responsible for the shoulders of the main peak of the real-space distribution function. The results are used to support validity of the method previously used to monitor thermal expansion of the glassy alloys using an X-ray diffraction profile. (c) 2006 Elsevier B.V. All rights reserved.

The glass-forming ability (GFA) of an alloy in this case is the largest diameter of a rod which can be cast fully glassy. The present work shows that the thermal conductivity of a liquid alloy has a strong effect on GFA by influencing the cooling rate upon mould casting. The initial cooling rates ( for the first 70 - 100 K of temperature decrease), obtained for Cu-, Zr- and Au-based bulk glass-forming alloys in the liquid state, are found to scale linearly with the thermal conductivities of the liquid base elements. However the low cooling rate found for Ni-based alloy suggests that the heat transfer at the melt - mould interface may also influence the cooling rate. The low thermal conductivity of Ni-based alloys and the correspondingly low cooling rate obtained compared to Cu- based counterparts explains their lower GFA. In the literature, many factors influencing the GFA of alloys have been discussed. To these factors, the present study adds the thermal conductivity of the molten alloy and the melt - mould heat-transfer coefficient. Moreover, the cooling rate depends on temperature and, thus, the critical cooling rate itself is not a suitable parameter for indicating GFA. The cooling can be better described by an appropriate fitting of the cooling curve to an exponential temperature decay function.

In this study, microwave (MW) heating of Fe powder in the separated electric (E-) and magnetic (H-) fields was performed first, and the heating behaviors on the field dependence were investigated. It was shown that they are heated better in H- field than in E- field. The MW heating mechanism of metals were briefly discussed. MW heating of soda-lime glass alone was not easy, however addition of iron powder enhanced the heating, depending on the volume fraction of the powder. Occurrence of deformation and melting of the glass spheres was observed. This technique is applicable to fabrication of glass-metal composites and vitrification of waste matters. MW heating of Ni-based metal glass was attempted with no external pressure and in an inert atmosphere, it was also shown that heating was better accomplished in H- field. Weakly sintered body was possibly obtained with retention of the amorphous phase.

The crystallization behavior and the structure of the welded samples of the Ni53Nb20Ti10Zr8Co6Cu3 glassy alloy are studied. A large supercooled liquid region of about 50K observed enables its successful welding. On heating the supercooled liquid crystallizes by polymorphous mechanism forming a single metastable hR14 Ni4Ti3 phase which further transforms at higher temperature forming several equilibrium phases. Its composition was found to be very close (equal within the confidential interval) to that of the glassy phase. The kinetic analysis confirmed the interface-controlled polymorphous transformation mechanism observed. Good bonding between two glassy samples was obtained after welding. The results indicate that with an increase in the welding speed from 2 to 3 m/min the structure of the welded zone changes from the amorphous + hR14 Ni4Ti3 crystalline phase to an almost single amorphous one. By adjusting the welding speed one can obtain the desired microstructure. The samples electron-beam welded at the beam current of 4 mA and voltage of 60 kV at a speed of 4 m/min were found to be almost amorphous. The results indicate successful welding of the Ni-based glassy samples.

Porous bulk metallic glasses recently attract increasing scientific and industrial attention due to their unique mechanical, physical, chemical, thermal, electrical and acoustic properties. In the present study, porous Zr55Cu30Al10Ni5 bulk metallic glass specimens were fabricated by a spark plasma sintering process using the Zr55Cu30Al10Ni5 glassy alloy powders made by argon gas atomization method. No crystallization was observed in the sintered porous bulk glassy alloy. The thermal stability of the sintered porous glassy alloy specimen was similar to that of the original powder. The sintered porous glassy alloy specimen exhibited larger plastic ductility and lower Young's modulus than those of the as-cast alloy specimen.

A spark plasma sintering technique was successfully used to consolidate Zr(55)Cu(30)Al(10)Ni(5) bulk metallic glassy matrix composite containing Al(2)O(3) particulates. No crystallization of the glassy matrix occurred during the spark plasma sintering process. The Al(2)O(3) particles were homogeneously dispersed in the Zr(55)Cu(30)Al(10)Ni(5) glassy matrix. The crystallization behavior of the sintered composite was similar to that of the metallic glassy powder. A large compressive strength of the sintered composite specimens was exhibited.

The structure of a Zr-Cu-Ni-Al glassy sample, successfully welded with an electron-beam technique, is investigated. The results indicate that the weld bead retains its glassy structure, though some medium range order zones appear to form after welding, while the heat-affected zone lying 1-2 mm from the weld bead contains a small fraction of oblong nanocrystals 1-3 nm in width. The results represent successful welding of glassy samples.

In the current paper, we review our recent studies and present new data on Ge- and Si-based amorphous and composite alloys containing nanoscale semiconductive Ge or Ge(Si) solid solution particles homogeneously distributed in a conductive amorphous matrix formed by rapid solidification or by devitrification of an amorphous single phase. Ge-rich alloys containing up to 70 at.% Ge were produced in Ge-Al-Cr-RE (RE, rare earth elements) systems, while Si-based amorphous alloys containing up to 60 at.% Si were produced in Si-Al-TM (TM, transition metals) systems by the melt-spinning technique. The samples are ribbons 10-100 mu m thick. Nanocomposites in Si-Al-TM-Ge and some Ge-Al-Cr-RE alloys were produced directly by rapid solidification, while in the Ge55Mg35Y10 alloy they were produced by devitrification of the glassy phase on heating. The semiconductive nanoparticles exhibit homogeneous distribution, and their sizes vary from similar to 5 nm to 20 nm. The structure, phase transformations, and properties of the samples are discussed.

We have successfully fabricated porous Zr55Cu30Al10Ni5 bulk metallic glassy alloy samples using a spark plasma sintering process. No crystallization was observed in the sintered porous alloy. The porosity was controlled by the sintering temperature and loading pressure. The sintered porous alloy exhibited a larger plastic ductility and lower Young's modulus than the as-cast specimen. These unique characteristics of the porous bulk glassy alloy indicate the possibility of its future applications as a new structural and functional material. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The present paper aims to compare the deformation-induced crystallization behavior of the rapidly solidified ribbon samples of Al85Y8Ni5Co2,Al85Nd8Ni5Co2, Al85Gd8Ni5Co2 and Al(85)Mm(8)Ni(5)Co(2) non-crystalline alloys subjected to cold rolling with 33% reduction. It is found that amorphous Al95Y8Ni5Co2 alloys exhibiting glass-transition and Al85Nd8Ni5Co2 alloys exhibiting no glass-transition have somewhat different stabilities against crystallization under deformation at room temperature though their crystallization temperatures under heating without load or deformation are almost equal. Al85Gd8Ni5Co2 and Al(85)Mm(8)Ni(5)Co(2) alloys (Mm = Mischmetal) did not exhibit deformation-induced crystallization at the reduction ratio used. Although, the formation of the primary nanoscale alpha-Al particles was observed in both Al85Y8Ni5Co2 and Al85Nd8Ni5Co2 alloys after the cold rolling, the size and volume fraction of the particles are larger in the Nd-bearing amorphous alloy as compared to the Y-bearing alloy. It is found that contrary to crystallization on heating no intermetallic compounds but only alpha-Al nano particles were formed during the deformation-induced crystallization of Al85RE8Ni5Co2 amorphous alloys. The local heating on deformation is hypothesized to affect the crystallization. (c) 2006 Elsevier B.V. All rights reserved.

The effect of electron irradiation on the structure of melt-spun Cu50Zr45Ti5 metallic glass was investigated. Microstructural evolution during electron irradiation was examined by means of conventional and high-resolution transmission electron microscopy (CTEM and HRTEM) equipped with X-ray energy dispersive spectroscopy (EDS). The glassy phase was not stable under electron irradiation and crystalline nanoparticles with the monoclinic CuZr structure were formed. The volume fraction of the nanocrystalline phase increased with the electron dose while the average grain size remained at about 7 nm. This result indicates that electron irradiation is effective in producing nanocrystalline structures from the metallic glass.

An as-solidified structure of an Al-based ribbon sample produced by the melt-spinning technique was studied by x-ray diffractometry and transmission electron microscopy. The addition of Pd to Al-Y-Ni-Co alloys caused formation of the highly dispersed primary α-Al nanoparticles about 3-5 nm in size homogeneously embedded in the glassy matrix upon solidification. The first direct observation of microstrain and dislocations quenched in nanoparticles with a size below 7 nm is provided. © 2006 Materials Research Society.

A composite nanostructure consisting of Pt nanoparticle/W nanodendrite was fabricated on an insulator Al2O3 substrate using an electron-beam-induced deposition process combined with an ion sputtering method. W nanodendrites with the tips of 3 nm were grown self-standing at the edge of the Al2O3 substrate. The observed morphology is attributed to a growth mechanism involving an electrical charge-up on the substrate surface, movement of charges, and their accumulation on the convex surface of the substrate as well as at the tips of the deposits. Pt nanoparticles with an equilibrium face-centered-cubic structure were uniformly distributed on the W nanodendrites. These composite nanostructures have potential for application in the fields of catalysis and nanodevices. (c) 2006 American Institute of Physics.

In the present letter we compare the thermal conductivities of Cu- and Ni-based alloys in relation with their cooling rates and glass-forming abilities. The cooling rates obtained for Cu- and Ni-based bulk glass-forming alloys are found to scale with the thermal conductivities of the base elements. Relatively low thermal conductivity of Ni-based alloy compared to the Cu-based one explains its lower glass-forming ability. The results also indicate that the thermal conductivity of the molten alloy should be also used as an indicator of the glass-forming ability among the other factors. (c) 2006 American Institute of Physics.

High-strength nonequilibrium hypereutectic bulk alloys were obtained recently in the Ti-Fe and Ti-Fe-Co systems by arc-melting. Following these results, the influences of the additional alloying elements (V, Ni, Cu, Sn, B) on high strength hypereutectic Ti-Fe-Co bulk alloys are studied and analyzed in the present work. The structure of the hypereutectic quaternary Ti(67)Fe(14)C0(14)Sn(5), Ti67Fe14Co14V5, Ti70Fe17Co7Cu6, Ti70Fe17CoNi6, and Ti69.4Fe14.8Co14.8B1 alloys obtained in the form of arc-melted ingots of about 20-30 rum diameter and 10-15 mm height was studied by X-ray diffractometry and scanning electron microscopy. The mechanical properties were tested by an Instron-type machine. Ti67Fe14Co14Sn5 alloy exhibits a high ultimate compressive strength of 1830 MPa and a large plastic strain of 24% which exceeds the ductility values obtained for Ti-Fe and Ti-Fe-Co alloys. The addition of Sn causes formation of a relatively rough eutectic structure which is preferable for the high strength hypereutectic alloys. Rough primary dendrites and eutectic rods of the cP2 intermetallic phase act as efficient barriers for shear strain and cracks propagation while fine eutectic rods of submicron size are quite effortlessly cut by deformation bands and cracks. (c) 2005 Elsevier Ltd. All rights reserved.

Thermal expansion of a glassy Cu55Hf25Ti15Pd5 alloy studied by using reciprocal space functions is verified using a real-space pair distribution function. The experimental results obtained by real-time diffraction during heating in a synchrotron beam and their Fourier transformation processing to derive radial distribution functions indicate that both reciprocal and real-space distribution functions give good agreement in the calculation of thermal expansion data. In addition to providing structural information, these findings indicate that the change in the average atomic nearest-neighbor distance evaluated from the variation of the position of the main broad diffraction maximum can provide good thermal expansion data for metallic glasses.

The influence of the electronegativity difference among the constituent elements on the stability of the supercooled liquid in two Al-based glassy alloys is studied. A record-large value of the supercooled liquid region of about 50 K is obtained based on the electronegativity difference concept within a certain composition range. (c) 2006 American Institute of Physics.

We found that a Ni-rich alloy with the composition of Ni50Pd30P20, had high glass-forming ability. Bulk glassy alloy rods with diameters up to 7 mm can be easily formed by a water quenching method. Its mechanical properties were measured under compressive load. The bulk glassy alloy exhibits relatively high yield strength of 1780 MPa and good ductility as is evidenced from a large plastic elongation of 7.6% before final fracture. The elastic properties of this bulk glassy alloy were also investigated.

The present work is devoted to an investigation of the composition of a nanoscale icosahedral phase in a Cu55Zr30Ti10Pd5 glassy alloy by three-dimensional atom probe analysis. The data indicate that the composition of the nanoicosahedral phase that precipitates from the Cu55Zr30Ti10Pd5 glassy alloy is not much different from that of the matrix, that is, the icosahedral phase is Cu-based containing more than 50 at. % Cu. The formation criteria for Cu- and Zr/Hf-based icosahedral phases are discussed based on quasi-lattice constant derived from average atomic diameter ratio. (c) 2005 American Institute of Physics.

The formations of glassy and supercooled liquid phases in Ni-Nb-Zr-Ti, Ni-Nb-Zr-Ti-Pt and Ni-Nb-Zr-Ti-Pt-Cu alloys were studied by using X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. It is found that the additions of Pt and Cu increase the supercooled liquid region of Ni-Nb-Zr-Ti alloy from 42 to 89 and 91 K, respectively. The increase in the supercooled liquid region is achieved mostly because T-x rises more intensively than T-g with Pt content. Quite low liquidus temperature of about 1300 K and high T-g value of about 850 K obtained for the studied alloys lead to a high T-g/T-1 ratio which reaches 0.65 and favors the glass-forming ability. Nucleation and growth of Ni4Ti3 and Ni-10(Zr,Ti)(7)(ss) phases takes place from the supercooled liquid in Ni60Nb10Zr15Ti15 and Ni52.5Nb10Zr15Ti15Pt7.5 alloys. (c) 2005 Elsevier Ltd. All rights reserved.

The phase transformations in a rapidly solidified (Fe0.75Pt0.25)(75)B-25 alloy on heating were studied by X-ray diffractometry, differential scanning and isothermal calorimetries. An as-solidified structure was examined by transmission electron microscopy (TEM). The results of TEM, including nano-beam diffraction and high-resolution imaging, clearly indicate the existence of nano-scale cubic cF4 Fe(Pt) solid solution particles within the as-solidified amorphous matrix. The particles of the cF4 Fe(Pt) phase start growing at elevated temperature and undergo ordering forming a tP4 FePt compound followed by the precipitation of a tI12 Fe2B phase from the residual amorphous matrix. The ordering of the cubic phase takes place after an incubation period which allows to anticipate a nucleation and growth mechanism. This process is followed by further growth of the particles. The transformation behavior on heating is studied in detail. (c) 2005 Elsevier B.V. All rights reserved.

The icosahedral quasicrystalline, amorphous plus crystalline and glassy phases were formed in Ti40Zr20Hf20(3d-LTM)(20) alloys (3d-LTM = 3d late transition metals Fe, Co and Ni). The icosahedral phase formed in the melt-spun Ti40Zr20Hf20Fe20 alloy is metastable and the average size of the quasicrystalline icosahedral particles precipitated in the amorphous matrix is 5 nm. The metastable icosahedral phase transformed to a big-cubic fcc Hf2Fe phase with the grain size of about 20 nm after annealing for 1.8 ks at 841 K. The glassy phase was formed in the melt-spun Ti40Zr20Hf20Co20 alloy and no metastable phase was found to form during the transformation from glassy phase to a stable crystalline phase. Icosaheadral phase formed in the melt-spun Ti40Zr20Hf20Ni20 alloy transformed to a big-cubic fcc (Zr,Ti)(2)Ni solid solution phase by a solid state reaction. (c) 2005 Elsevier B.V. All rights reserved.

An as-solidified structure and transformation behaviour on heating of the rapidly solidified Al-Y-Ni-Co-Pd alloy was studied by X-ray diffractometry (XRD), transmission electron microscopy (TEM), differential scanning and isothermal calorimetries. The Al-Y-Ni-Co-Pd ribbon samples have been produced by the melt spinning technique and heat treated using a differential scanning calorimeter (DSC). The addition of Pd to Al-Y-Ni-Co alloys caused disappearance of the supercooled liquid region as well as the formation of the highly dispersed primary α-Al nanoparticles about 3-7 nm in size homogeneously embedded in the glassy matrix upon solidification. An extremely high density of precipitates of the order of 1024 m-3 is obtained. These particles start growing at the temperature below a glass-transition temperature. The results presented in this paper indicate that some of so-called "marginal" glass-formers in as-solidified state are actually not glassy alloys with pre-existed nuclei but crystal-glassy nanocomposites. © 2005 Elsevier B.V. All rights reserved.

A nanoscale icosahedral (I) phase was formed in the melt-spun Ti40Zr20Hf20(LTM)(20) (LTM = Ni, Pd, or Pt) alloys. However, in Pd-bearing alloy it is presumed to be a distorted I-phase or a high-order approximation. I phase, Hf2Pt and beta-(Ti, Zr, Hf, Ni) solid solution phases are formed in the arc-melted Ti40Zr20Hf20Pt20 ingot. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Thermal expansion and volume changes due to structural relaxation during heat treatment in glassy alloys were studied in situ using Synchrotron X-ray radiation diffractometry. A glass transition phenomenon was also detected. Synchrotron X-ray radiation diffractometry was successfully used for studying dilatation, glass transition and volume change phenomena detecting excess free volume and in glassy alloys. Good correspondence of the thermal expansion coefficients was obtained independently by thermomechanical length change measurements and Synchrotron X-ray radiation diffractometry as well as the glass transition temperature obtained by DSC and Synchrotron X-ray radiation diffractometry. The reduced average free volume change is smaller in the alloy consisting of the glassy matrix containing the nanocrystalline phase compared to the fully glassy alloy. (c) 2005 Elsevier B.V. All rights reserved.

High-strength Ti-Fe-Co alloys were produced in the shape of arc-melted ingots with the dimensions of about 20-25 mm in diameter and 7-10 mm in height. The structure of the Ti-Fe-Co alloys (at Fe/Co ratio &gt; 1) studied by X-ray diffractometry and scanning electron microscopy consisted of an ordered Pm3m Ti(FeCo) compound and a disordered body-centered cubic Im3m beta-Ti solid solution. The optimization of the Ti-Fe-Co alloy composition is performed from the viewpoint of both high strength and ductility. The strongest Ti-Fe Co alloys have a hypereutectic structure and exhibit a high strength of about 2000 MPa and a plastic deformation of 15%. The high strength and ductility values can be achieved without using the injection mould casting or rapid solidification procedure. The deformation behavior and the fractography of Ti-Fe-Co alloys are studied in detail. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

An amorphous phase was formed for (Fe0.75Pt0.25)(100-x)B-x (x = 25 and 30) alloys by melt-spinning. Their crystallization temperature were 671 and 667 K, respectively. The amorphous alloys exhibited good soft magnetic properties. The crystallized structure consisted of gamma(1)-FePt (fct), Fe2B and gamma-FePt (fee) phases, and their average grain sizes were about 15 nm after annealing at 785 K for 900 s. The remanence (B-r), reduced remanence (M-r/M-s), coercivity (iH(c)) and maximum energy product (BH)(max) were 0.96 T, 0.83, 340 kA/m and 102.2 kJ/m(3), respectively, for the 25 at%B alloy, and 0.91 T, 0.82, 368 kA/m and 96.5 kJ/m(3), respectively, for the 30 at%B alloy. The reversible demagnetization loop behavior was also confirmed. Consequently, the good hard magnetic properties are interpreted as resulting from exchange magnetic coupling among nanoscale hard gamma(1)-FePt and soft Fe2B and gamma-FePt magnetic phases.

The devitrification of Ni60Nb25Ti15 glassy alloy has been investigated by X-ray diffraction (XRD), differential scanning and isothermal calorimetry and transmission electron microscopy (TEM). The primarily crystallized phase was a cubic Ni(Ti,Nb) phase with a lattice parameter of 0.293 nm. A Ni3Nb phase follows precipitation of the Ni(Ti,Nb) phase. The cubic Ni(Ti,Nb) phase undergoes partial transformation to Ni4Ti3 phase. These cubic Ni(Ti,Nb) phases disappear at the equilibrium conditions. The supercooled liquid region (Delta T-x) of the Ni60Nb25Ti15 glassy alloy was extended to 64 K with the addition of Pt. The Ni55Nb25Ti15Pt5 glassy alloy rods with diameters up to 2 mm were formed by mold casting. Pt and the other noble metals additions do not alter devitrification of Ni60Nb25Ti15 glassy alloy.

From the quaternary Ti-Zr-Hf-Ni phase diagram. the cross-section at 20 at % Ni was selected for investigation. The icosahedral quasicrystalline, crystalline and amorphous phases were observed to form in nine kinds of rapidly solidified (TixZryHfz)(80)Ni-20 (x + y + z = 1) alloys at different compositions. The quasilattice constants of 0.519 and 0.531 nm were obtained for the icosahedral phase formed in the melt-spun Ti40Zr20Hf20Ni20 and Ti20Zr40Hf20Ni20 alloys. respectively. The icosahedral phase formed in the melt-spun Ti40Zr20Hf20Ni20 alloy especially is thermodynamically stable. The supercooled liquid region of the Ti20Zr20Hf40Ni20 glassy alloy reached 64 K. From these results a comparison of quasicrystal-forming and glass-forming abilities, was carried out. The quasicrystal-forming ability was reduced and glass-forming ability was improved with an increase in Hf and Zr contents in the (TixZryHfz)(80)Ni-20 alloys. On the other hand. an increase in Ti content caused an improvement in quasicrystal-forming ability. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

We have determined changes in thermal expansion coefficient αth and relaxation behavior of glassy materials by monitoring the first maximum of the diffraction pattern, obtained in transmission during in-situ heating in a high-intensity high-energy monochromatic light beam. The excess quenched-in free-volume ΔVf and its relaxation kinetics can also be determined. Like metallic glasses, oxide glasses also show the glass transition Tg with excess free-volume trapped during cooling. The results allow quantitative determination of Tg by diffraction that compares well with Tg obtained by calorimetry as was previously reported for metallic glasses and the relaxation of excess free volume.

The present work is devoted to an investigation of the formation of the nanoscale icosahedral phase in Cu55Zr30Ti10Pd5 and Cu50Zr30Ti10Pd10 bulk glassy alloys by synchrotron x-ray radiation. Calculations based on the x-ray and selected-area electron diffraction patterns indicate that this phase has a high degree of icosahedral order. Kinetics of the devitrification of Cu55Zr30Ti10Pd5 is also studied in detail. (C) 2005 American Institute of Physics.

In the present work we report on the formation of the high-strength and ductile hypo-, hyper- and eutectic Ti-Fe arc-melted alloy ingots with the dimensions of about 25-30 mm. in diameter and 10-15 mm in height. The structure of the samples studied by X-ray diffractometry and scanning electron microscopy is found to consist of cubic Pm (3) over barm TiFe and BCC Im (3) over barm. beta-Ti supersaturated solid solution phase. The arc-melted Ti65Fe35 alloy has a dispersed hypereutectic structure consisting of the primary TiFe phase and submicron-size eutectic structure. The arc-melted Ti65Fe35 alloy ingot sample exhibits excellent mechanical properties: a Young's modulus of 149 GPa, a high mechanical fracture strength of 2.2 GPa, a 0.2 % yield strength of 1.8 GPa and 6.7 % ductility. The hard round-shaped intermetallic TiFe phase and the supersaturated beta-Ti solid solution result in a high strength of the Ti65Fe35 alloy which in addition has much higher ductility compared to that of the nanostructured or glassy alloys. The ductile beta-Ti solid solution phase enables plastic deformation of the sample. The reasons for the high ductility of the hypereutectic alloy are discussed.

Structure and mechanical properties of binary Ti-TM (TM-other transition metals) and ternary Ti-Fe-(TM, B or Si) alloys produced in the shape of the arc-melted ingots of about 25 mm diameter and 10 mm height are studied. The formation of high-strength and ductile hypereutectic alloys was achieved in the Ti-Fe, Ti-Fe-Cu and Ti-Fe-B systems. The structures of the high-strength and ductile hypereutectic alloys studied by X-ray diffractometry and scanning electron microscopy were found to consist of the primary cubic Pm (3) over barm intermetallic compound (TiFe-phase or a solid solution on its base) and a dispersed eutectic consisting of this Im (3) over barm intermetallic compound + BCC Im (3) over barm beta-Ti supersaturated solid solution phase. The hypereutectic Ti-Fe alloy showed excellent compressive mechanical properties. The addition of Cu improves its ductility. B addition increased mechanical strength. Ni, Cr and Mn additions caused embrittlement owing to the formation of alternative intermetallic compounds. The deformation behaviour and the fractography of the Ti-based alloys were studied in details. The reasons for the high strength and good ductility of the hypereutectic alloys are discussed.

The present work is devoted to the study of a number of binary Ti-TM (TM-other transition metals) and ternary Ti-Fe-(TM, Al, B or Si) as well as Ti-Fe-RE (RE-rare-earth) alloys and reports on the formation of high-strength and ductile hypereutectic Ti-Fe, Ti-Fe-Cu and Ti-Fe-Nd alloys in the form of arc-melted ingots about 25 mm diameter and 10 mm height. Structures of the high-strength and ductile hypereutectic alloys studied by X-ray diffractometry and scanning electron microscopy were found to consist of the primary cubic Pm 3 m intermetallic compound (TiFe-phase or a solid solution on its base) and a dispersed eutectic consisting of this Pm 3 m intermetallic compound + BCC Im 3 m beta-Ti supersaturated solid solution phase. The hypereutectic Ti-Fe alloy showed excellent compressive mechanical properties. The addition of Cu and Nd improves its ductility. B addition increased mechanical strength. Ni, Cr and Mn additions caused embrittlement owing to the formation of alternative intermetallic compounds. The deformation behaviour and the fractography of the Ti-based alloys were studied in details. The reasons for the high strength and good ductility of the hypereutectic alloys are discussed.

In the present work we report on the formation of the high-strength and ductile hypo-, hyper- and eutectic Ti-Fe arc-melted alloy ingots with the dimensions of about 25-30 mm. in diameter and 10-15 mm in height. The structure of the samples studied by X-ray diffractometry and scanning electron microscopy is found to consist of cubic Pm (3) over barm TiFe and BCC Im (3) over barm. beta-Ti supersaturated solid solution phase. The arc-melted Ti65Fe35 alloy has a dispersed hypereutectic structure consisting of the primary TiFe phase and submicron-size eutectic structure. The arc-melted Ti65Fe35 alloy ingot sample exhibits excellent mechanical properties: a Young's modulus of 149 GPa, a high mechanical fracture strength of 2.2 GPa, a 0.2 % yield strength of 1.8 GPa and 6.7 % ductility. The hard round-shaped intermetallic TiFe phase and the supersaturated beta-Ti solid solution result in a high strength of the Ti65Fe35 alloy which in addition has much higher ductility compared to that of the nanostructured or glassy alloys. The ductile beta-Ti solid solution phase enables plastic deformation of the sample. The reasons for the high ductility of the hypereutectic alloy are discussed.

This overview paper summarizes a large number of data connected with nano-devitrification of metallic glassy and amorphous alloys on heating which form nanoscale crystalline or quasicrystalline particles. In some alloys this effect leads to formation of the nanocomposites with enhanced mechanical properties compared to fully glassy and crystalline alloys. Copyright © 2005 American Scientific Publishers All rights reserved.

Nonlinear viscoelasticity influenced by an <i>in situ</i> nanocrystallization under constant load compression at the glass transition temperature, <i>T</i><SUB>g</SUB>, is investigated with a Cu<SUB>60</SUB>Zr<SUB>30</SUB>Ti<SUB>10</SUB> (at %) bulk metallic glass (BMG). The experimental curves showed the characteristics, softening and subsequent recovering phenomena which have been observed in a &lsquo;stable&rsquo; Zr-based BMG and also hardening through whole deformation process due to the <i>in situ</i> nanoprecipitation in the glass matrix. These characteristics are fairly reproduced by the fictive stress model extended by the Johnson-Mehl-Avrami (JMA) equation and mixture rule for respectively expressing influences of the Newtonian viscosity and of Young's modulus and critical stress on volume fraction of the nanoprecipitates.

The structure of hypoeutectic, hypereutectic, and eutectic Ti-Fe alloys produced in the shape of arc-melted ingots was found to consist of the ordered Pm-3m TiFe and disordered BCC Im (3) over barm beta-Ti solid solution phase. The dimensions of the ingots were about 25-40 mm in diameter and 10-15 mm in height, and their structure was studied by x-ray diffractometry and scanning electron microscopy. The rectangular parallelepiped-shaped samples 2.5 x 2.5 x 5 mm in size cut from the central part of the ingots exhibit a high strength of about 2000 MPa, except for Ti60Fe40, and a certain ductility. The relatively low density of Ti (4.5 Mg/m(3)) implies high strength/density ratio for the studied alloys. These alloys are characterized by the low cost of the alloying element Fe and, compared to most of the high-strength non-equilibrium materials, do not require additional injection mold casting or rapid solidification procedures.

Microstructure and magnetic properties of melt-spun Fe80-xPtxB20 (x=20,22,24) alloy ribbons have been investigated. A homogeneous nanoscale mixed structure with amorphous and fcc gamma-FePt phases was formed in the melt-spun ribbons. The average sizes of the amorphous and fcc gamma-FePt phases are about 5 nm, and the enrichment phenomenon of B is recognized in the coexistent amorphous phase. The melt-spun ribbons exhibit soft magnetic properties. The nanocomposite structure consisting of fct gamma(1)-FePt, fcc gamma-FePt, and Fe2B phases was obtained in the melt-spun ribbons annealed at 798 K for 900 s, and their average grain sizes are about 20 nm. The remanence (B-r), reduced remanence (M-r/M-s), coercivity (H-i(c)), and maximum energy product (BH)(max) of the nanocomposite alloys are in the range of 0.93-1.05 T, 0.79-0.82, 375-487 kA/m, and 118-127 kJ/m(3), respectively. The good hard magnetic properties are interpreted as resulting from exchange magnetic coupling between nanoscale hard fct gamma(1)-FePt and soft magnetic fcc gamma-FePt or Fe2B phases. (C) 2004 American Institute of Physics.

The "fragile"-"strong glass" transition in Al-based alloys is observed as a function of Sc content. The Sc-bearing alloys suffer glass transition as well as Sc-free Al0.84Y0.09Ni0.05Co0.02 alloy, however, the value of DeltaC(p) decreases drastically and comes within the variation of the baseline at higher than 2 at. % of Sc. The studied glasses are free from pre-existing nuclei. (C) 2004 American Institute of Physics.

The formation of the supercooled liquid region and devitrification behavior of Ni-based glassy alloys were studied by using X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. oC68 Ni10Zr7-type phase is primarily formed in the studied alloys in the initial stage of the devitrification process by nucleation and three-dimensional diffusion controlled growth. The replacement of Cu by Ni in Cu55Zr30Ti10Pd5 glassy alloy induces precipitation of oC68 Ni10Zr7 phase directly from the glassy phase. The reasons for such a behavior are discussed taking into account mixing enthalpy in a liquid state and the interval of the supercooled liquid region. (C) 2004 Elsevier B.V. All rights reserved.

The devitrification behavior and phase formation in Zr65-55Ni10Al7.5Cu7.5Ti5-10(Nb,Ta)(5-10) metallic glass have been studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. It has been found that mutual addition of Ti and Ta/Nb benefits the formation of nanoscale icosahedral phase in the glassy phase on heating and the oxygen content in the alloy makes significant influence on the devitrification behavior of these alloys. At the same time in Nb-bearing alloys and alloys containing 5 at.% Ta icosahedral phase was found to coexist with crystalline one. (C) 2004 Published by Elsevier Ltd.

Crystallisation behaviour and magnetic properties of as-spun and annealed Fe40Co40Cu0.5Zr9Al2Si4B4.5 alloy have been studied. The annealing was performed at 873 K for 15 min. XRD and TEM studies shows the formation of nanocrystalline alpha-(Fe,Co)(SiAl) particles with 7.5+/-2nm in diameter dispersed in an amorphous matrix. The Curie temperature of the as-spun amorphous ribbon is 736 K. Saturation magnetisation of the annealed sample decreases at a rate of 0.5 emu/g/K in the measured temperature range of 300-1000 K. Excellent room temperature AC magnetic properties are achieved for the nanocrystalline sample. The low value of the imaginary part of the permeability and the high cut-off frequency (20 kHz) suggest that the eddy current contribution in the annealed materials is low. The coercivity of the annealed sample remains almost constant at 95 A/m up to the frequency of 20 kHz. High saturation magnetisation, high Curie temperature and excellent soft magnetic properties in the nanocrystalline state suggests that Fe40Co40Cu0.5Zr9Al2Si4B4.5 alloy is a strong candidate for high temperature magnetic application. (C) 2004 Elsevier B.V. All rights reserved.

Recently new Hf-based multicomponent amorphous alloys have been developed based on empirical rules for large glass forming ability. These ribbons were obtained by melt-spinning a master alloy, composed of Group IVB elements (Ti, Zr, Hf) of the Periodic Table with additions of late transition metals such as Cu or Ni. One of the best known bulk glass-forming alloy systems is based on (Zr/Ti)-(Cu/Ni)-Al, the addition of Al of the IIIA group with sp electrons and strong interactions with Zr is a key factor in reducing the critical cooling rate for glass formation. Hf is chemically similar to Zr but has a much higher melting temperature. Characterization of the as-quenched (Hf/Zr/Ti)-(Cu/Ni)-(Al/Ga)-(Si/Ge) ribbons was carried out by X-ray diffraction and the thermal stability was followed by differential scanning calorimetry and differential thermal analysis. (C) 2003 Elsevier B.V. All rights reserved.