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High temperature deformation was probed in a La-based high entropy metallic glass with an evident slow β relaxation. The correlation between high configurational entropy and high temperature deformation mechanism was analyzed. On the one hand, by increasing the strain rate, the degree of deviation from Newtonian behavior in high entropy metallic glasses is lower than that of conventional metallic glasses, which is ascribed to the high configurational entropy. On the other hand, high configurational entropy leads to a decrease in activation volume in high temperature deformation of metallic glasses. Identifying the influence of high configurational entropy on the deformation mechanism paves the way for further understanding of the mechanical behavior of metallic glasses. [ABSTRACT FROM AUTHOR]

Glass transition is one of the unresolved critical issues in solid-state physics and materials science, during which a viscous liquid is frozen into a solid or structurally arrested state. On account of the uniform arrested mechanism, the calorimetric glass transition temperature (Tg) always follows the same trend as the dynamical glass transition (or α-relaxation) temperature (Tα) determined by dynamic mechanical analysis (DMA). Here, we explored the correlations between the calorimetric and dynamical glass transitions of three prototypical high-entropy metallic glasses (HEMGs) systems. We found that the HEMGs present a depressed dynamical glass transition phenomenon, i.e., HEMGs with moderate calorimetric Tg represent the highest Tα and the maximum activation energy of α-relaxation. These decoupled glass transitions from thermal and mechanical measurements reveal the effect of high configurational entropy on the structure and dynamics of supercooled liquids and metallic glasses, which are associated with sluggish diffusion and decreased dynamic and spatial heterogeneities from high mixing entropy. The results have important implications in understanding the entropy effect on the structure and properties of metallic glasses for designing new materials with plenteous physical and mechanical performances. Here the authors study thermodynamic and dynamic glass transition of high entropy metallic glasses. Results show retarded α-relaxation and distinct crystallization resistance attributed to their sluggish diffusion and high-entropy mixing that is different from the traditional metallic glasses. [ABSTRACT FROM AUTHOR]

Ti40Zr10Cu36Pd14 Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications thanks to its high glass forming ability, the absence of toxic elements such as Ni, Al or Be and its good mechanical properties. For the first time, a complete and exhaustive characterization of a unique batch of this glassy alloy was performed, together with ISO standard mechanical tests on machined implant-abutment assemblies. The results were compared to the benchmark Ti-6Al-4V ELI (Extra-Low-Interstitial) to assess its potential in dental implantology. The thermal stability, corrosion and sterilization resistance, cytocompatibility and mechanical properties were measured on samples with a simple geometry, but also on implant-abutment assemblies’ prototypes. Results show that the glassy alloy exhibits a quite high thermal stability, with a temperature range of 38 °C between the glass transition and crystallization, a compressive strength of 2 GPa, a certain plastic deformation (0.7%), a hardness of 5.5 GPa and a toughness of 56 MPa.√m. Moreover, the alloy shows a relatively lower Young’s modulus (96 GPa) than the Ti-6Al-4V alloy (110–115 GPa), which is beneficial to limit bone stress shielding. The BMG shows a satisfactory cytocompatibility, a high resistance to sterilization and a good corrosion resistance (corrosion potential of −0.07 V/SCE and corrosion current density of 6.0 nA/cm2), which may ensure its use as a biomaterial. Tests on dental implants reveal a load to failure 1.5-times higher than that of Ti-6Al-4V and a comparable fatigue limit. Moreover, implants could be machined and sandblasted by methods usually conducted for titanium implants, without significant degradation of their amorphous nature. All these properties place this metallic glass among a promising class of materials for mechanically-challenging applications such as dental implants. [ABSTRACT FROM AUTHOR]

In this paper, in-situ β-Ti phase reinforced (Al, Ni, Be)-free Ti-based bulk metallic glass matrix composites (BMGMCs) were developed by microalloying Mo. The BMGMCs showed higher fracture strength and larger plastic strain than the monolithic glassy counterpart and other Be-free Ti-based BMGMCs, under both compression and bending tests. The ductile and soft β-Ti secondary phase appeared to hinder the rapid propagation of the main shear band, improving the plasticity. Furthermore, the size and interparticle spacing of the secondary β-Ti were very close to the processing zone size, further stabilizing the shear band against developing into cracks and thus improving mechanical properties. But under tension, no obvious ductilization was observed for the BMGMCs, maybe resulting from the lower volume fraction of β-Ti phase because of higher cooling rate during the fabrication for them. Further work should be focused on optimizing the composition and increasing the volume fraction of β-Ti phase and sample size. [ABSTRACT FROM AUTHOR]

In-situ Ti-reinforced Mg-based (MT-D) and in-situ Ta-reinforced Zr-based (ZT-D) bulk metallic glass matrix composites (BMGMCs) were prepared by a novel dealloying method, which contains an element-selective leaching process in a metallic melt. The BMGMCs exhibit better mechanical properties, including higher fracture strength and larger plastic strain, than their monolithic glassy counterparts or similar BMGMCs by ex-situ dispersing or conventional arc-melting methods. The differences of Young's modulus between the dispersoids and the glassy matrix for these BMGMCs generate stress concentration at the interface, which is considered to suppress the propagation of the single main shear band and initiate multiple shear bands to accommodate the plastic deformation. Furthermore, the fine size of dispersoids for these BMGMCs, caused by low reaction temperature during dealloying in the metallic melt, results in more interfaces with the matrix for further improvement of mechanical properties. In addition, the low reaction temperature can also contribute to less composition fluctuation of the matrix to maintain the glass-forming ability of itself, which can introduce no undesired phases to degrade the mechanical properties. This novel in-situ dealloying method is believed to make a breakthrough in designing ductile BMGMCs with fine-sized secondary particles. [ABSTRACT FROM AUTHOR]

Abstract: The shear banding behavior and fracture mechanisms of a Zr55Al10Ni5Cu30 bulk metallic glass (BMG) were investigated using uniaxial compression tests equipped with a digital image correlation (DIC) method system. The DIC results captured the shear bands correctly, and the Zr-based BMG exhibited two deformation modes depending on the strain rate. In the fast mode under a strain rate of 1.0 × 10−2 s−1, multiple shear banding was observed. The effects of shear band interactions were observed in the DIC results, and the results were analyzed in terms of the serrated plastic flow. The stair shaped fracture pattern and slipped vein pattern found on the fracture surface were strong evidence of the shear band interactions. However, the plastic deformation was confined to a few shear bands without shear band interactions in the slow mode under a strain rate of 1.0 × 10−4 s−1. From quantitative analyses, it was found that the shear bands propagated progressively rather than simultaneously at the beginning of the shear band formation. Then, the propagation became simultaneous after the shear band formation was completed through the entire shear planes. This progressive propagation behavior caused strain heterogeneity, which increased after each reactivation event. Also, two shear bands propagated simultaneously without interactions in the direct observations, which represented a load drop in serrated flow. Furthermore, it was revealed that there were different fracture mechanisms depending on the strain rate and deformation mode. This comprehensive quantitative analysis of the shear banding behavior and fracture mechanisms of BMGs enables better understanding and design of superior BMGs. [Copyright &y& Elsevier]

Abstract: A significant enhancement in plasticity was achieved by the micro-addition of Cu in Fe-based bulk metallic glasses (BMGs) which have high strength at room-temperature. It was found that the nanocrystallization caused by the formation of the α-Fe phase is responsible for the improvement in plasticity of the Fe-based BMGs. Our results suggest that the micro-addition of Cu is a promising approach to enhancing the plasticity of Fe-based BMGs through compositional and structural design by microalloying. [Copyright &y& Elsevier]

Abstract: In the glassy temperature region from the ambient to glass transition temperature, an apparent Young''s modulus (E ap), the slope of the initial linear part on the stress–strain curve, in a Zr-based metallic glass clearly depends on both temperature and strain rate, indicating that viscous contribution is included in the elastic response. Because the yield stress depends on temperature and strain rate as the same manner with E ap, the yield strain was found to keep the “universal” critical strain ∼0.020 for many metallic glasses at the ambient temperature. This suggests that the yield phenomenon is simply dominated by E ap. [Copyright &y& Elsevier]

Abstract: Magnetic properties of (Fe0.72B0.24Nb0.04)95.5Y4.5 sample were investigated. The sample was produced from glassy powders made by the gas-atomization and consolidation using the spark plasma sintering (SPS) technique. Maximum relative density of 99.5% was achieved in the spark plasma sintered (SPSed) compact due to the viscous flow enhanced by the applied stress even under the glass transition temperature. X-ray diffraction pattern of the compact indicates that the glassy structure was maintained through the SPS process. However, the results of differential scanning calorimetry (DSC) showed that the glass transition temperature and crystallization temperature of the SPSed glassy compact shift to a higher and lower temperature, respectively, that is, a smaller ΔT x. Saturation magnetization of the SPSed glassy compact became 10% higher than that of the initial glassy powder. The Curie point was enhanced from 522K for the glassy powder to 548K for the SPSed glassy compact. Spin-exchange interaction is expected to be enhanced by a short-range scale atomic rearrangement caused by the high applied stress and temperature during the SPS process. [Copyright &y& Elsevier]

Abstract: Mg-based bulk metallic glass matrix composite with hcp-Ti powders was fabricated by casting the mixtures of Mg65Cu25Gd10 molten alloy and pure Ti powders into a copper mold. Ti powder was spherical and less than 150μm in diameter, and its volume fraction was controlled from 5 to 40%. Thermal stability of the glassy matrix was maintanied even in the coexistence with the Ti powders. However, Ti dispersoid caused a significant improvement on compressive ductility from 0% plastic deformation for the monolithic glass to 41% plastic deformation for the composite with 40vol.% Ti powders. This is the first success of synthesizing Mg-based alloys with high ultimate strength of ∼900MPa level as well as the large plastic deformation of ∼40%, and suggests a novel guideline to develop Mg-based alloys having high specific strength with high ductility. [Copyright &y& Elsevier]

Abstract: Both mechanical (stress, strain, and viscosity) and thermal (specimen temperature) behaviors during nonlinear viscoelastic processes, i.e., softening and the following recovery phenomena, which were observed experimentally during constant load compressions in a Zr55Al10Ni5Cu30 bulk metallic glass at the glass transition region, were calculated using the fictive stress model. Although the model contains several approximations for simplification, the simulated results fit well with the experimental curves. This model has good potential as a tool for designing an adequate near-net shaping condition for glassy materials in the supercooled liquid state to avoid devitrification during processing. [Copyright &y& Elsevier]

Abstract: Multi-component (Cu0.50Hf0.35Ti0.10Ag0.05)100− x Ta x (x =0, 1, 3, 5, 8, 12) bulk metallic glass (BMG) composites containing in situ formed dendrites were prepared successfully. With increasing Ta content, both compressive fracture strength (σ f) and elastic-plastic strain (ε f) increase from 2180MPa and 2.1% for x =0, to 2770MPa and 19.2% for x =8, respectively, but yield strength and elastic modulus decrease. The precipitation of a high volume fraction of the dendrites (V dendrite) causes the compositional variation of the dendrites and its counterpart glass matrix. Composition analysis shows that both Hf and Ti elements exhibit an opposite behavior of dissolving into the dendrites during the cooling. About 7–11at.% component elements (Ti, Cu and Ag) were detected in Ta-rich dendrites, but no Hf element was found. With increasing V dendrite, the content of component elements dissolving into Ta-rich dendrites decreases from 11.35at.% for V dendrite =4.3% and 7.97at.% for V dendrite =26.5%. Indentation testing was also performed to evaluate the properties of the composites. With increasing V dendrite, the hardness of the dendrites decreases from 6.0GPa for x =3 to 5.21GPa for x =12, and its elastic modulus increases from 151.2GPa for x =3 to 156.9GPa for x =12. The hardness and elastic modulus of the glassy matrix also decrease, respectively, from 9.66 and 148.7GPa for x =0 to 9.36 and 137.4GPa for x =12 with increasing precipitation of the dendrites. The variation of the properties is due to the compositional change originating from the opposite behavior of Hf and Ti elements to dissolve into the dendrites. [Copyright &y& Elsevier]

The primary transformation reaction of the Zr65Al7.5Cu27.5 ternary glassy alloy with a low oxygen impurity of approximately 100 mass ppm was investigated. We have discovered the precipitation of the metastable icosahedral phase with a fine grain size of 50-100 nm in diameter accompanying with the formation of stable Zr2Cu phase at the annealing temperatures ranging from 715 to 730 K. The lattice spacing of Zr2Cu phase decreases at higher temperatures, which is attributed to the rearrangement of Zr and Cu in the decomposition of the icosahedral phase. It is suggested that the formation of the icosahedral phase in the primary stage originates from the existence of the quenched-in icosahedral local atomic configuration in the glassy state. [ABSTRACT FROM AUTHOR]

Finite element analysis of a stress-overshoot phenomenon in a Pd-based bulk metallic glass was carried out using a fictive stress model in conjunction with the Maxwell viscoelastic model under uniaxial compression. The overshoot results from non-linear viscoelasticity in the glass transition region, under deformation at constant strain rate. The friction effect between a cylindrical workpiece and a die was shown to produce mainly three stress-concentration sites, which play an important role in creating free volume. These sites give rise to a redistribution of the structural disordering state inside the workpiece, and lead to a change of the average stress blunt. Once inhomogeneous deformation occurs during the development of the stress peak at the initial stages under high strain rates (5 × 10-3–2.2 × 10-2 s-1), the effective stress distribution within the workpiece becomes narrow and the deformation homogeneity is recovered in the ensuing steady state flow. [Copyright &y& Elsevier]

The evolution of specific heat of a Pd40Ni40P20 glassy alloy subjected to different degrees of non-Newtonian flow condition near the glass transition temperature, Tg, was investigated by a differential scanning calorimetry (DSC) method. Three exothermic relaxation spectrums were observed in temperature dependence of the specific heat. One of the relaxations in T>490 K (=Tg-95 K) strongly depended on the flow condition, on the other hand, the others did weakly. This relaxation has previously been reported to be due to the long-range disordering between metal and metalloid constituents. The local atomic structure causing the non-Newtonian flow is therefore expected to show modification among metal and metalloid elements. Using a X-ray diffraction method followed radial distribution function analysis, this modification is observed. [Copyright &y& Elsevier]

Mechanical properties and fracture characteristics of Zr-based bulk metallic glass (BMG) composites containing carbon nanotube (CNT) addition were investigated in detail. The interfacial reaction between the added CNTs and the glass matrix causes the formation of some V-shape nicks on the residual CNTs. These nicks have significant effect on the mechanical properties and fracture modes of the BMG composites. The compressive fracture strength increases with increasing the volume fraction of CNT addition at first, and starts to decrease gradually when the volume fraction of CNT addition is more than 5.0%. The fracture modes of the BMG composites also change from typical shear flow deformation behavior to completely embrittling fracture gradually. The V-shape nicks originating from the interfacial reaction are responsible for the decrease of fracture strength and the variation of fracture modes. [ABSTRACT FROM AUTHOR]

The mechanical properties, glass-forming ability, supercooled liquid region and devitrification behaviour of the Cu–Zr–Ti–(Pd, Ag, Pt and Au) bulk glass formers were studied by using a mechanical testing machine, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. The bulk glassy alloys of diameter 2 mm were formed in the Cu55Zr30Ti10Pd5 and Cu55Zr30Ti10Ag5 alloys while Cu55Zr30Ti10Au5 bulk alloy showed mixed glassy and crystalline structure. No glassy phase was formed in the Cu55Zr30Ti10Pt5 bulk alloy whereas the glassy phase was formed in all of the ribbon samples prepared by rapid solidification. The studied alloys except for the Pt-bearing one have slightly increased compressive fracture or yield strength values compared to ternary Cu60Zr30Ti10 glassy alloy. At the same time Pd and Au addition significantly expand the supercooled liquid region of Cu–Zr–Ti glassy alloy and increase Young''s modulus. A nanoicosahedral phase is primarily formed in the Cu55Zr30Ti10(Pd,Au)5 glassy alloys in the initial stage of the devitrification process by nucleation and three-dimensional diffusion-controlled growth. Nearly the same quasilattice constant obtained in the Cu55Zr30Ti10(Pd,Au)5 alloys illustrates the same type of the icosahedral phase in these alloys. However, no icosahedral phase was found in the Cu55Zr30Ti10(Ag,Pt)5 alloys. [Copyright &y& Elsevier]

The correlation of quasistatic and dynamic relaxations was discussed in a typical strong Zr55Al10Ni5Cu30 metallic glass from room temperature to Tg. The quasistatic relaxation behavior, investigated by high temperature compressive testing at a constant strain rate, was compared with dynamic tensile relaxation behavior. A correlation equation of the dynamic frequency and quasistatic strain rate was successfully deduced, and then its validity was experimentally confirmed in a fragile metallic glass. Using this correlation, the Cox–Merz rule, derived for correlating the steady-state and dynamic viscosities of the polymers, is found to be applicable to metallic glasses. [ABSTRACT FROM AUTHOR]

Abstract: In the glassy temperature region from ambient to the glass transition temperature (T g), an apparent Young''s modulus (E ap), the slope of the initial linear part on the stress–strain curve, in a Zr-based metallic glass clearly depends on both temperature and strain rate, especially above 0.87 T g. This indicates that viscous contribution is included in this apparent elastic response. If yield strain is deduced with Young''s modulus measured by the ultrasonic vibration method, which excludes the viscous contribution, temperature dependence of the yield strain can be captured well with the Argon''s Shear Transformation Zone (STZ) model. On the other hand if the yield strain is deduced with E ap, the strain was found to keep the “universal” critical value ∼0.020 for many metallic glasses at the ambient temperature. This may indicate another clue to understand the yield mechanism on BMG. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

A single Zr65Al7.5Ni10Pd17.5 bulk metallic glass exhibits a large plastic strain of 6.6% during the compressive deformation process, which is attributed to the deformation mode with nanoscale multistep shear bands. We have observed that nanocrystals with a metastable fcc Zr2Ni structure containing several distorted icosahedral clusters are arranged in a “bandlike” formation in the glassy matrix around the multistep shear bands. This is recognized as direct evidence of the novel phenomenon of the restraint of shear band propagation owing to the dynamic precipitation of the nanocrystals. [ABSTRACT FROM AUTHOR]

The influences of sample diameter (D), Pd content (x), and hydrostatic pressure (P) in a chamber during casting on the structure of as cast Zr65Al7.5Ni10Cu17.5-xPdx(x=10, 17.5 at.%) bulk alloys were investigated. Zr65Al7.5Ni10Cu7.5Pd10 and Zr65Al7.5Ni10Pd17.5 alloys (D=3 mm) cast in a vacuum chamber (P∼4.0×10-3 Pa) were mainly of the tetragonal-Zr2Ni equilibrium phase and nanosize icosahedral primary phase, respectively, while the same alloys cast in inert argon gas at atmospheric pressure (P∼0.1 Mpa) were of the single glassy phase. Due to the higher cooling rate obtained by decreasing the sample diameter (D=2 mm) even in the vacuum chamber, the Zr65Al7.5Ni10Pd17.5 alloy was still of the icosahedral phase, while the Zr65Al7.5Ni10Cu7.5Pd10 alloy froze into a single glassy phase. These results indicate that the temperature- and timetransformation curves for the icosahedral and subsequent equilibrium phase formations in the alloy system shifts to a shorter time side with decreasing P, and the pressure sensitivity of the icosahedral phase formation increases with x. [ABSTRACT FROM AUTHOR]

The heat evolution of stress-induced structural disorder, ΔH[sub s]([variant_greek_epsilon]), of a Zr[sub 55]Al[sub 10]Ni[sub 5]Cu[sub 30] bulk metallic glass (BMG) during compressive constant ram-velocity deformation at the glass transition region (T[sub g]=680 K) was deduced from in situ measurements of temperature change of the deforming sample. At the transition from the linear to nonlinear viscoelasticity, the behavior of viscosity change with strain, η([variant_greek_epsilon]), is qualitatively consistent with the enthalpy evolution of the structural disordering, ΔH[sub s]([variant_greek_epsilon]), but not with the temperature change, ΔT([variant_greek_epsilon]). It is concluded that the initial softening deformation is due to the stress-induced structural disordering. The change in the nonlinearity, -log η ≡-log η /η[sub N], is found to be proportional to the ΔH[sub s] and the slope of ΔH[sub s](-log η) can be estimated to 400 J/mol, where η[sub N] is the Newtonian viscosity. On the other hand, the temperature raise, ΔT([variant_greek_epsilon]), is pronouncedly delayed as compared with the η ([variant_greek_epsilon]) and ΔH[sub s]([variant_greek_epsilon]) at the transition, but is determined by a product of stress and plastic strain-rate, σ·[variant_greek_epsilon][sub p], and is nearly proportional to it at the steady state. The slope of ΔT(σ·[variant_greek_epsilon][sub p]) can be estimated to 5.2×10[sup -2] K mol/W. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Reports the production of full strength compacts of metallic glass by warm extrusion of powders. Alloy used in the production of compacts; Temperature for maintaining the ductility of melt-spun alloy; Conduction of powder production and its consolidation in a closed powder metallurgy processing system.

The present work was aimed to demonstrate the possibility of forming Fe66Cr10Nb5B19 metallic glass coatings by detonation spraying and analyze the coating formation process. A partially amorphous Fe66Cr10Nb5B19 powder with particles ranging from 45 µm to 74 µm in diameter was used to deposit coatings on stainless steel substrates. The deposition process was studied for different explosive charges (fractions of the barrel volume filled with an explosive mixture (C2H2 + 1.1O2)). As the explosive charge was increased from 35% to 55%, the content of the crystalline phase in the coatings, as determined from the X-ray diffraction patterns, decreased. Coatings formed at explosive charges of 55–70% contained as little as 1 wt.% of the crystalline phase. In these coatings, nanocrystals in a metallic glass matrix were only rarely found; their presence was confined to some inter-splat boundaries. The particle velocities and temperatures at the exit of the barrel were calculated using a previously developed model. The particle temperatures increased as the explosive charge was increased from 35% to 70%; the particle velocities passed through maxima. The coatings acquire an amorphous structure as the molten particles rapidly solidify on the substrate; cooling rates of the splats were estimated. The Fe66Cr10Nb5B19 metallic glass coatings obtained at explosive changes of 55–60% showed low porosity (0.5–2.5%), high hardness (715–1025 HV), and high bonding strength to the substrate (150 MPa). [ABSTRACT FROM AUTHOR]

Even though the Mg-based bulk metallic glasses (BMGs) have shown superior anti-corrosion properties compared with their crystalline counterparts, the brittleness of them limits the widespread application of these materials. In the present study, we have firstly introduced porous NiTi shape memory alloy particles into an Mg-Zn-Ca BMG by the direct adding method. This composite showed both improved compressive strength and corrosion resistance in Hank's solutions than its monolithic glassy counterpart. The NiTi dispersoids among the matrix were likely to hinder the main shear band propagation, and also acted as the corrosion barriers. Furthermore, the porous nature of present added particle could further increase the interface areas, which should enhance the reinforcing effects compared with solid ones. This low-cost, high-anticorrosive composite was a good candidate as an engineering material. [ABSTRACT FROM AUTHOR]

Abstract Biomaterials are attracting an ever-increasing research interest. As part of this overall effort, we report herein the fabrication and characteristics of Zr-based ribbon samples with three different compositions: Zr 56 Co 28 Ga 16 , Zr 56 Co 28 Ga 14 Si 2 , and Zr 56 Co 28 Ga 14 Sn 2. The supercooled-liquid region Δ T = T x − T g of these materials is 16, 18, and 29 K, respectively, where T x is the temperature of the onset of crystallization and T g is the glass-transition temperature. The samples are thermally characterized by using differential scanning calorimetry and by determining the activation energy. The corrosion resistance is determined by immersing the materials for up to 20 days in a simulated body fluid, and the cytotoxicity is measured from the proliferation of osteoblast-like cells on the samples. Finally, the mechanical properties are investigated by nanoindentation. The Young's modulus is 112 GPa. These results all highlight the suitability of this metallic glass for biomedical applications. Highlights • A new, Zr-based metallic glass was elaborated as biomaterials, without Fe, Ni or Al. • Replacing Al by Ga was investigated and biocompatibility of the alloy is promising. • This Zr-glass exhibits a good thermal stability and good corrosion resistance. • Additions of Si/ Sn in the system increase corrosion resistance and biocompatibility. • Young modulus is lower than that of common crystalline alloys used as biomaterials. [ABSTRACT FROM AUTHOR]

In the present study TiNb/Zr 55 Cu 30 Al 10 Ni 5 with various fraction additions were fabricated by spark plasma sintering successfully. The interface between the TiNb and the glassy matrix was investigated by nanoindentation. The results indicate that there is a good bonding between them. Therefore, the strength and plastic strain are improved due to introduction of TiNb. In order to study the improved plastic deformation of the composites, the FEM (Finite Element Method) was adopted. It is observed that more shear bands are formed around the TiNb particles. The shear bands form and propagate at the interface of the TiNb and the glassy matrix due to the misfit of their Young's modulus, therefore, the plastic strain is improved. [ABSTRACT FROM AUTHOR]

Bulk metallic glassy composites reinforced by ZrO 2 with various volume fraction and particle size were fabricated successfully by spark plasma sintering. The compression test results indicate that mechanical property of composite is related to the particle size and volume fraction of ZrO 2 . Due to the stress concentration between the ZrO 2 and the glassy matrix, both the plastic strain and fracture strength increase firstly and then decrease with the increase of volume fraction of ZrO 2 . The deformation morphologies of composites after compression reflect the ductile–brittle transition process. [ABSTRACT FROM AUTHOR]

The degradation behavior and hydrogen evolution reaction (HER) performance of nano-porous PdPtCuNiP (NP-PdPtCuNiP) high entropy metallic glass in 65℃ 0.5 mol L−1 H 2 SO 4 electrolyte was investigated. For electrolytic system shutdown condition, the corrosion effect would lead the dissolution of Ni, Cu and P from NP-PdPtCuNiP surface, and form a Pd-Pt binary alloy catalytic surface. Meanwhile, the input power fluctuation resulting in incomplete cathodic protection of the cathode. The corrosion on cathode surface caused the surface constituent and morphology changed, and the surface condition is affected by power frequency. Finally, an in-situ repair strategy for degraded cathode is proposed. • Selective dissolution of NP-PdPtCuNiP leading to the degradation of catalytic surface. • Triangle power accelerated the reconstruction of NP-PdPtCuNiP cathode surface. • A potentiostatic repair strategy for degraded NP-PdPtCuNiP electrode is established. [ABSTRACT FROM AUTHOR]

Abstract: Large glassy alloy discs (12mm diameter, 1mm thickness) of high relative density (∼98%) were prepared by spark plasma sintering. The bulk magnetic cores (12mm outer diameter, 6mm inner diameter, 1mm thickness) exhibit good soft magnetic properties: saturation magnetization is 1.44T, coercivity is 31A/m, and effective permeability at 1kHz is 1320. They also exhibit much lower loss than a silicon steel core; core loss at 10kHz and maximum induction of 0.2T is only 81.7W/kg. [Copyright &y& Elsevier]

Abstract: The effect of Mo addition on the glass-forming ability (GFA), magnetic properties, mechanical properties and corrosion resistance of (Fe0.76Si0.096B0.084P0.06)100−x Mo x (x =0, 2, 4 and 6at.%) bulk glassy alloys (BGAs) with high Fe contents was investigated. The 2at.% Mo addition makes the alloy composition approach towards a eutectic point, which could result in an increase in the GFA. The BGA rod with diameters up to 3.5mm was produced by copper mold casting. These BGAs exhibit a rather high saturation magnetization of 0.98–1.51T and lower coercive force of 1.7–2.1A/m. A significant improvement in corrosion resistance was observed with microalloying Mo element in 1N H2SO4 solution. Furthermore, these Fe-based BGAs show super-high strength of ∼3.3GPa and Young''s modulus of 200GPa. [Copyright &y& Elsevier]

Abstract: 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 (∼90%) is formed. This new insight on flow behavior opens up possibilities for innovative processing of precise bulk shapes with high nanocrystal densities. [Copyright &y& Elsevier]

Aiming to unraveling the effects and mechanisms of Nb and Fe additions on glass-forming ability (GFA) and magnetic properties, especially coercivity (H c) on Co-based metallic glasses, 2–4 at% Nb and/or 7.15–28.6 at% Fe have been alloyed into a Co 71.5 Gd 3.5 B 25 alloy by substitution of Co. The results show that alloying either Nb or Fe into the base alloy leads to enhanced stability of supercooled liquid and GFA, and bulk metallic glass (BMG) can be formed for the alloy with 4 at% Nb or 28.6 at% Fe. Combined addition of Nb and Fe further improves the thermal stability and GFA, and lowers viscosity in supercooled liquid state. A (Co 0.6 Fe 0.4) 67.5 Gd 3.5 Nb 4 B 25 BMG possess a wide supercooled liquid region (Δ T x) of 85 K, critical sample diameter of 3.0 mm, and minimum viscosity coefficient of 2 × 108 Pa∙s. The enrichment of Fe increases saturation magnetic flux density (B s), H c , and saturation magnetostriction coefficient (λ s) of the (Co, Fe)-Gd-B-(Nb) metallic glasses; the addition of Nb effectively inhibits the deterioration of magnetic softness caused by Fe while reducing the B s. The (Co 0.6–0.9 Fe 0.1–0.4) 67.5 Gd 3.5 Nb 4 B 25 BMGs possess good soft magnetic properties with the B s and H c ranging 0.43–0.69 T and 2.3–5.0 A/m, respectively. Ab initio molecular dynamics simulations indicated that alloying Fe into the Co-based metallic glasses leads to enhanced magnetic anisotropy energy. The increased magnetic anisotropy arising from enlarged λ s results in the increased H c. The combination of high GFA, large Δ T x , low viscosity, and good soft magnetic properties makes the Co-based Co-Fe-Gd-Nb-B BMGs highly promising for applications as micro electromagnetic devices produced through thermoplastic forming. • New soft magnetic Co-based Co-Fe-Gd-Nb-B bulk metallic glasses have been developed. • The BMGs exhibit a combination of high GFA and good thermal stability and soft magnetic properties. • The mechanism of increased coercivity of the Co-based BMGs after Fe addition has been revealed. [ABSTRACT FROM AUTHOR]

Photoemission and inverse-photoemission spectroscopy (PES and IPES) measurements were carried out on Zr 50 Cu 50 , Zr 45 Cu 45 Ag 10 , and Zr 40 Cu 40 Ag 20 metallic glasses to investigate the valence- and conduction-band electronic structures, respectively. From the incident photon energy, hν , dependence of the PES spectra, partial DOSs of s and d electrons for the constituent elements were estimated, and it was found that the DOS near E F is mainly composed of Zr 4 d electrons and the Cu 3 d electrons are localized in the valence band. Core-level PES measurements were also performed at the Zr 3 d , Cu 3 p , and Ag 3 d levels. The Zr 3 d core spectra indicate three chemical states in all of these glasses, suggesting a chemical heterogeneity. Energy shifts are observed in the Zr 3 d core levels, indicating the charge transfer in the Zr-Cu-Ag metallic glass system. [ABSTRACT FROM AUTHOR]

Ti40Zr10Cu36Pd14 Bulk Metallic Glass (BMG) appears very attractive for future biomedical applications thanks to its high glass forming ability, the absence of toxic elements such as Ni, Al or Be and its good mechanical properties. For the first time, a complete and exhaustive characterization of a unique batch of this glassy alloy was performed, together with ISO standard mechanical tests on machined implant-abutment assemblies. The results were compared to the benchmark Ti-6Al-4V ELI (Extra-Low-Interstitial) to assess its potential in dental implantology. The thermal stability, corrosion and sterilization resistance, cytocompatibility and mechanical properties were measured on samples with a simple geometry, but also on implant-abutment assemblies’ prototypes. Results show that the glassy alloy exhibits a quite high thermal stability, with a temperature range of 38 °C between the glass transition and crystallization, a compressive strength of 2 GPa, a certain plastic deformation (0.7%), a hardness of 5.5 GPa and a toughness of 56 MPa.√m. Moreover, the alloy shows a relatively lower Young’s modulus (96 GPa) than the Ti-6Al-4V alloy (110–115 GPa), which is beneficial to limit bone stress shielding. The BMG shows a satisfactory cytocompatibility, a high resistance to sterilization and a good corrosion resistance (corrosion potential of −0.07 V/SCE and corrosion current density of 6.0 nA/cm2), which may ensure its use as a biomaterial. Tests on dental implants reveal a load to failure 1.5-times higher than that of Ti-6Al-4V and a comparable fatigue limit. Moreover, implants could be machined and sandblasted by methods usually conducted for titanium implants, without significant degradation of their amorphous nature. All these properties place this metallic glass among a promising class of materials for mechanically-challenging applications such as dental implants. [ABSTRACT FROM AUTHOR]

As part of a project to develop new and more performant types of metallic glass (MG) for use in biomedical applications, we developed a new ribbon-metallic glass with two different compositions, Mg (85 − x) Ca (8 + x) Au 7 (with x = 0, 2, 4) and Mg (81 − x) Ca 10 Au 7 Yb (2 + x) (with x = 0, 8). The super-cooled liquid region was evaluated to be ΔT = Tx − Tg = 22 °C, where Tx is the temperature of crystallization and Tg is the glass transition temperature. The thermal stability of this material was investigated using different measurement methods. No crystallization was detected after 30 min at 120 °C, which is of major interest for sterilization processes in the medical field. Resistance to crystallization was also investigated. All the results highlight the suitability of this new metallic glass for biomedical applications. [ABSTRACT FROM AUTHOR]

Addition of a small amount of La and Co enhances the stabilization of supercooled liquid and glass-forming ability (GFA) of an Al 85 Ni 7 Er 8 metallic glass. The Al 85 Ni 5 Co 2 Er 6 La 2 alloy exhibits large supercooled liquid region of 40 K, high GFA with a critical thickness of 450 μm, and the viscosities on the order of 10 7 −10 9 Pa s in the supercooled liquid state. The Al-based glassy nano-scale patterns were formed by imprinting, indicating its good thermoplastic formability. The possible mechanism for the improvement of the supercooled liquid stability of the Al Ni Er alloy by addition of La and Co elements was discussed in terms of the crystallization behavior. [ABSTRACT FROM AUTHOR]

Metallic glass (MG) exhibits viscous flow behavior in the supercooled liquid (SCL) state, which is of great advantage for its net-forming process. However, the viscous workability varies strongly with the alloy system and/or composition. In this paper, we demonstrate how MG with less viscous workability such as Gd-based MG can be processed in the SCL region. Based on this understanding, high aspect ratio analyzer gratings of 9 μm pitch and ∼30 μm heights have been fabricated through an imprinting method by allowing crystallization during a rapid heating isochronal imprinting process. The analyzer gratings made of Gd-based MG have brought a breakthrough for advancing neutron phase imaging based on grating interferometer. [ABSTRACT FROM AUTHOR]

• Glass-forming ability of Pd-based metallic glasses is studied in relation to the hyper-ordered structures • Characteristic features are observed by Voronoi tessellation and persistent homology analyses • Structures of excellent Pd 42.5 Ni 7.5 Cu 30 P 20 are compared with those of Pd 40 Ni 40 P 20 and Pd 40 Cu 40 P 20 in detail [Display omitted] To understand the relation of the glass-forming ability (GFA) to the local atomic configurations of a Pd 42.5 Ni 7.5 Cu 30 P 20 (PNCP) metallic glass having the best GFA at present, the local structures were investigated by combining data obtained from anomalous X-ray scattering, X-ray and neutron diffraction, and applying reverse Monte Carlo modeling. By comparing the results of PNCP with Pd 40 Ni 40 P 20 (PNP) and Pd 40 Cu 40 P 20 (PCP) having a slightly and much worse GFAs, respectively, characteristic features were observed in the hyper-ordered atomic structures. Firstly, the concentration inhomogeneity of Ni/Cu in PNCP is larger than that of Ni in PNP and Cu in PCP. Secondly, a Voronoi tessellation showed that the fraction of pure icosahedral arrangements around the Cu atoms increases significantly in PNCP by adding icosahedral-preferred Ni atoms in PCP. Finally, a persistent homology (PH) analysis reveals the largest intermediate-size Cu PH rings in PNCP among the PH rings in these Pd-based BMGs. The structural heterogeneity for the excellent GFA of PNCP would be considered by an incompatible mixture of specific Pd-P configurations and icosahedral clusters around the secondary Ni and Cu metals. [ABSTRACT FROM AUTHOR]

Soft magnetic Co-based bulk metallic glasses (BMGs) with large supercooled liquid region (Δ T x) of 47 K and high saturation magnetic flux density (B s) up to 1.21 T have been developed in a new Co-Fe-B-P-C alloy system without early transition metal and rare earth elements. Substitution of Co by 10–35 at.% Fe in a Co 75 B 10 P 7.5 C 7.5 alloy promotes the occurrence of glass transition and enhances the stability of supercooled liquid and glass-forming ability (GFA). The Δ T x of 37–47 K and a critical sample diameter up to 1.2 mm can be achieved for Co 40 – 55 Fe 20 – 35 B 10 P 7.5 C 7.5 BMGs. The improved thermal stability and GFA are attributed to complicated primary crystallization phases and stabilized alloy melts, respectively. The addition of Fe enhances the B s of the Co-based BMGs from 0.79 to 1.21 T, and increases coercivity from 1.1 to 7.2 A/m. The Co-based BMGs also exhibit high yield strength of 3243–3665 MPa with plastic strain up to 2.3% and low viscosity of around 3.0 × 109 Pa·s in the supercooled liquid state. • Soft-magnetic Co-based BMGs have been developed in a new Co-Fe-B-P-C alloy system. • The Co-based BMGs have large supercooled liquid region of 47 K and B s up to 1.21 T. • Replacement of Co with Fe improves thermal stability and GFA of Co-B-P-C metallic glasses. [ABSTRACT FROM AUTHOR]

Thedynamics of Pd-based metallic glass-forming liquids (Pd40Ni10Cu30P20, Pd42.5Ni7.5Cu30P20, Pd40Ni40P20, and Pd30Ni50P20)was studied by mechanical spectroscopy and modulated differentialscanning calorimetry (MDSC). We found that the change in compositionhas a significant effect on the α relaxation dynamics; the largestdifference corresponds to an increase of the glass transition temperature Tgof ∼15 K, for materials in which 30%Ni was substituted by 30% Cu (i.e., from Pd40Ni40P20to Pd40Ni10Cu30P20). We also found that all Pd-based metallic glasses havevery similar fragilities, 59 < m< 67, andKohlrausch stretched exponents, 0.59 < βKWW<0.60. It is interesting that the values of mandβKWWcorrelate well with the general relation proposedby Böhmer et al. for nonmetallic glass formers (Böhmer,R.; et al. J. Chem. Phys.1993, 99, 4201–4209), which for the observed βKWWvalues predicts 58 < m< 61. Froma linear deconvolution of the α and β relaxations, wefind that the substitution of the Ni with Cu induced a large changein the time constant of the Johari–Goldstein relaxation, τβ. The activation energy, Uβ, of the β relaxation was largely independent of chemical composition.In all cases, 25 < Uβ/RT< 28, a range in agreement with results for otherglass formers (Kudlik, A.; et al. Europhys. Lett.1997, 40, 649–654 and Ngai,K. L.; et al. Phys. Rev. E2004, 69, 031501). From the heat capacity and mechanical loss,estimates were obtained for the number of dynamically correlated units, Nc; we find significantly larger values for thesemetallic glass-forming liquids than Ncfor other glass-forming materials. [ABSTRACT FROM AUTHOR]

Abstract: A Mg3Cu3Gd bulk metallic glass matrix composite with porous α-Ti dispersoids was prepared by dealloying in a metallic melt. The in situ formed α-Ti dispersoids had a pore-size of ∼500nm, which was imparted from the Ti2Cu precipitate in the prealloy. Pore size was therefore controllable through the cooling rate of the prealloy preparation. Plasticity was not improved apparently, however the maximum fracture stress under four point bending mode increased from 217MPa for the monolithic counterpart to 387MPa. This was due to the optimal relationship where dispersoid size (L)≈dispersoid interval distance (S)≈process zone size (R p ). This was achieved locally within and around the porous Ti dispersoids, and helped improve the toughness and ductility. [Copyright &y& Elsevier]

• Nanoscale patterns were imprinted on FeCo-based metallic glass thin films. • A large mold fill factor was achieved for the imprinted patterns. • The thin-film magnetic properties were tailored by crystallization and the patterns. The ability to create submicron/nanoscale patterns with magnetic alloys at low cost is difficult. Here, we demonstrate a method to create such patterns using Fe 40 Co 35 P 10 C 10 B 5 metallic glass thin films. The viscous workability of a metallic glass thin film was used to make patterns with dimensions up to ~100 nm using the nanoimprinting technique, and the effects of the patterning on the magnetic properties of the metallic glass thin films were investigated. An increase in the out-of-plane coercivity (~380 Oe) and remanent magnetization (M r = ~12% of the saturation magnetization, M s) were observed for amorphous thin films patterned with a high density of nano-dots. This effect was observed because of changes to the magnetic shape anisotropy induced by the nano-imprinting. Two events of magnetization reversal were confirmed in the crystalline films of the same alloy. The reversal of magnetization under the low magnetic field of ~100 Oe corresponds to soft magnetic phases, whereas that at 2400 Oe corresponds to the hard magnetic phase. Recoil curve measurements suggest that the average magnetization-switching field of hard magnetic grains in the film was between 2800 and 3600 Oe. Based on our experimental results and analysis, we suspect the presence of tetragonal Fe–Co hard/semihard magnetic phase in crystalline thin films. We believe that the low-cost and large-area micro- to nanoscale patterning ability of the present magnetic thin films are promising for the development of various magnetic MEMS and memory devices. [ABSTRACT FROM AUTHOR]

Abstract: Friction welding of Zr-based bulk metallic glass (Zr55Al10Ni5Cu30 alloy) has been tried. Friction time and friction pressure were chosen as the control parameters for the friction welding process. Their influences on the shape and volume of the protrusion formed from the welded interface were investigated. Temperature distribution around the interface during friction welding was measured using an infrared thermal imager. Successful joining of Zr55Al10Ni5Cu30 BMG was accomplished through the precise control of friction time and friction pressure. Whether crystallization occurred or not during friction welding correlated to the volume of the protrusion formed at the welded interface. [Copyright &y& Elsevier]

• Glass-forming ability of metallic glasses is investigated by hyper-ordered structures. • Intermediate-range structures of Pd 40 Cu 40 P 20 are compared with those of Pd 40 Ni 40 P 20. • Important features are found in Voronoi tessellation and persistent homology analyses. To clarify the relationship between the glass- forming ability (GFA) and local atomic structure of Pd-based metallic glasses, the structures of an amorphous Pd 40 Ni 40 P 20 are investigated by anomalous X-ray scattering and neutron diffraction with help of reverse Monte Carlo modeling, and important structural features characteristic to the GFA are found in the hyper-ordered structures, such as persistent homology ring sizes, in comparison with those of Pd 40 Ni 40 P 20 glass. To clarify the relationship between the glass-forming ability (GFA) and local atomic structure of Pd-based metallic glasses, the structures of an amorphous Pd 40 Cu 40 P 20 (PCP) were investigated using the same methods as for Pd 40 Ni 40 P 20 (PNP) metallic glass, i.e., by a combination of anomalous X-ray scattering, X-ray and neutron diffraction, and reverse Monte Carlo modeling. From the comparison between the results of PNP with an excellent GFA and the PCP with a worse GFA, important features characteristic to the GFA are found in the hyper-ordered structures. Firstly, the compositional inhomogeneity of Cu in PCP is larger than Ni in PNP. Secondly, a Voronoi tessellation reveals that icosahedral arrangements are found with considerable probability around the Ni atoms in PNP, while a less existence around the Cu atoms in PCP. Thirdly, a persistent homology (PH) analysis shows smaller intermediate-size Cu PH rings in PCP than Ni PH rings in PNP. [ABSTRACT FROM AUTHOR]

• Substituting few percents of Cu in TiZrCuPd BMG improves its passive behavior. • Sn and Si elements play a beneficial role on the metallurgical quality of BMG. • Heterogeneity within solid solution and casting defects act as weakening sites. • Adding Sn and Si elements limit the susceptibility to pitting corrosion. In this work, the effect of substituting Cu with small amounts of Sn and Si on the passive behavior and pitting resistance of the bulk metallic glass Ti 40 Zr 10 Cu 36 Pd 14 was investigated. The Sn/Si substitution promoted homogenization of the solid solution and limited the presence of casting defects. In addition, unlike the heterogeneous passive film grown on TiZrCuPd, the passive films of the micro-alloyed materials were homogeneous, implying less sensitivity to film weakening and breakdown. Thus, alloying with small amounts of Sn and Si appears to be a viable approach to drastically improve the corrosion resistance of TiZrCuPd. [ABSTRACT FROM AUTHOR]