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The liquid metal dealloying (LMD) process enables the fabrication of porous metals with various chemical compositions. Despite its advantages, LMD still faces key challenges such as maintaining the high‐temperature molten metal bath for a prolonged time, avoiding the use of toxic etchants, and so on. To overcome these challenges, the study develops a water‐leachable and oxidation‐resistant alloy melt (AM) in Ca‐Mg binary system. Specifically, Ca72Mg28 eutectic AM is designed, which exhibits higher oxidation resistance and lower melting temperature compared to pure Mg, allowing LMD to be conducted in atmospheric conditions as well as temperatures >200 K lower. The AM also enables an innovative process to fabricate Ti foams with a hexagonal faceted surface structure by carefully manipulating the etching rate during the water etching process. This approach allows for the creation of foam with a surface area over 13% larger than that of foams with smooth surfaces via normal acid etching, potentially enhancing efficiency in applications such as electrodes for electrochemical systems or biomedical materials where increased cell adhesion can be beneficial. This study paves the way for efficiently manipulating the LMD process to fabricate metal foams with customized compositions and enhanced surface properties. [ABSTRACT FROM AUTHOR]

A different dependence of apparent glass-forming ability (GFA) on casting-atmosphere pressure is observed in a Zr65Al7.5Ni10Cu17.5-xPdx (x=0–17.5) alloy system. Low-Pd alloys (x<12.5) reveal low GFA dependence, while high-Pd ones (x>=12.5) show high GFA dependence on atmosphere pressure applied during casting. The phenomenon is suggested to originate from the fact that for the high-Pd alloys, the transformation region of supercooled-liquid to quasicrystalline phase is located at the low-temperature side of the undercooled-liquid region where the atmosphere-pressure dependence of cooling characteristic coincidently takes place. The on-cooling phase transformation in the alloy system and the cooling mechanism during mold-casting process are discussed comprehensively. [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]

A NiTi/Mg composite was fabricated using a method that combines top-down pore-forming and pressureless infiltration processes. The phase constituents of this simple composite are B2-NiTi, B19′-NiTi and Mg phases. Both the size and the distribution of the Mg-phase are fine and homogeneous. The composite has very high mechanical strength and damping capacity, ~1.2 and 1.5-fold higher than those of a similar composite with different microstructures, respectively. These behaviors are generally attributed to the high damping capacity of Mg, the physical continuity of the composite, and the homogeneous distribution of fine Mg-phase, which generate more interfaces, contributing to the damping capacity. This composite is considered a good candidate for use as a damping material in engineering applications. [ABSTRACT FROM AUTHOR]

In this paper, submicron-porous NiTi and NiTiNb shape memory alloys were firstly fabricated by a new top-down process, including solidified phase controlling and etching process. These porous alloys possessed fine pore size (∼0.4 μm) and homogeneous pore distribution. The mechanical properties of these porous alloys were similar to those prepared by conventional powder metallurgy techniques or bottom-up process. However, the damping capacity of the submicron-porous NiTi was ∼0.07 and 40% higher than the counterparts produced by the conventional powder metallurgy techniques. The damping capacity of the submicron-porous NiTiNb was ∼0.18 and 50% higher than its dense counterpart. The internal friction value at austenite state for submicron-porous NiTiNb was ∼0.04 and 200% higher than its dense counterpart, 300% higher than submicron-porous NiTi. The high damping capacity of these submicron-porous shape memory alloys was considered to be caused partly by their fine pore structures, which enhanced the stress concentration and the microplastic deformation or collapse of thin nodes. These porous shape memory alloys exhibited moderate stiffness as well as high damping capacity and high specific strength, making them good candidate as practical engineering damping materials. [ABSTRACT FROM AUTHOR]

Open-cell macroporous Fe, Cr and their alloys were prepared by dealloying with a metallic melt. By immersing (Fe, Cr)30Ni70 precursors in a Mg melt, Ni selectively dissolved into the Mg and the remaining components formed a bicontinuous structure. Analyses of the thermal coarsening in the melt reveal that evolution of the porous structure is controlled by interfacial diffusion between the melt and precursor solid. The underlying mechanism for the nanoporous structure formation is therefore the same as that in aqueous solution. [Copyright &y& Elsevier]

Surface-activated bonding (SAB) is a direct-bonding method which joins two cleaned surfaces of similar or dissimilar materials at room or low temperature. The practicability and joint quality, however, depend strongly on the smoothness and crystallographic orientation of the bonding surfaces. Supercooled liquid metal possessing high structural homogeneity of the amorphous state and excellent near-net-shape-forming ability may resolve the shortcomings. This work proposes surface-activated supercooled liquid brazing, i.e. a modified SAB technique utilizing supercooled liquid metal as a brazing-filler material. [Copyright &y& Elsevier]

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: This study was focused on improving the plastic properties of FeSiBP bulk metallic glasses (BMGs) by adding small amount of Cu (0.1–0.6%). BMGs with significant plastic strain of up to around 3.1% and a strength of 3.3GPa were obtained in our investigation. Multiple shear bands and related shear ledges were observed on the deformed specimen. The high plasticity is attributed to the nano-scale inhomogeneity that results from phase separation, which can hinder the propagation of shear bands, in effect promoting multiple shearing. The characteristic size of the α-Fe nanoparticles embedded in the glassy matrix changed with Cu content. Our results indicated a dependence between the plastic behavior and the size of the α-Fe nanoparticles. A higher Cu content resulted in an increase in the size of the α-Fe nanoparticles. Of all the samples tested in our investigation, the (Fe0.76Si0.096B0.084P0.06)99.9Cu0.1 alloy exhibited the best plastic properties. [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]

The high-entropy alloy (HEA) design strategy is effective for ultra-coarsening-resistant 3D interconnected materials developed by liquid metal dealloying (LMD). However, the fundamental understanding of the dealloying mechanism and structural evolution of multi-principal elements 3D structured materials is still missing. In this study, the microstructural evolutions of 3D interconnected HEAs in Mg matrix were investigated using two types of multiphase precursors, namely, arc-melted and homogenized ones. The precursors' microstructure greatly influences dealloying kinetics and dealloying mechanisms what, in its turn, determines the final morphology of the 3D interconnected HEAs in Mg matrix. First, the prior fcc phase was dealloyed faster than any other precursor phases at dealloying temperatures from 600 to 900 °C. Second, the dealloying kinetics was faster along precursor grain boundaries (GB) as compared with grain interior. This led to the formation of a unique layered composite structure due to the inhomogeneous dealloying along the fine lamellars' GB of the homogenized precursor. Moreover, governing orientation relationship between precursor and dealloying product depends on the LMD conditions, and it significantly affects the 3D interconnected grain structure. The fundamental understanding of the dealloying mechanisms will pave the way for customized morphology design of the 3D interconnected HEAs in metallic matrix with improved thermal stability and physical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

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: Heat evolution of stress-induced structural disorder ΔH s(ε) of a Zr55Al10Ni5Cu30 bulk metallic glass (BMG) during compressive constant ram-velocity deformation in the glass transition region (T g =680K) was deduced from in situ measurements of temperature change ΔT(ε) of deforming samples, where ε is true strain. At transition from the linear to nonlinear viscoelasticity, i.e., a softening phenomenon, viscosity η(ε) does not change consistently with ΔT(ε) but with ΔH s(ε). Therefore, it is concluded that the stress-induced structural disorder triggered this softening phenomenon. The viscous frictional heating of the softened alloy brings about the increase in ΔT, which also influences ΔH s. Because ΔT is determined by relationship between the power of the frictional heating and heat convection to the sample-surroundings, ΔH s and η can be positively controlled with varying thermal conductivity D of the surrounding materials, especially after the transition period. [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]

It is found that an increase in the hydrostatic chamber pressure (P) during the casting process suppresses the glass forming ability (GFA) of the Zr65Al7.5Ni10Cu17.5 alloy, on the contrary, it enhances the GFA of the Zr65Al7.5Ni10Pd17.5 alloy. This opposite dependence of the GFA on P in these alloys may be because the volume increases or decreases by the primary crystallization. [Copyright &y& Elsevier]

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 structure of an arc-melted ingot of the Ti50Ni20Cu20Nb10 alloy of about 30 mm diameter and 10 mm height was studied by X-ray diffractometry, transmission electron microscopy (TEM). Mechanical properties were tested by an Instron-type testing machine. The ingot sample has a disperse submicron-size complex eutectic structure (including ternary eutectic) consisting of a quaternary β-(Ti, Nb, Ni, Cu) solid solution, a monoclinic TiNi-type (Ti, Nb)(Ni, Cu) phase and a (Ti, Nb)2(Cu, Ni) phase which is a solution of Nb (replacing Ti) and Ni (replacing Cu) in the tetragonal Ti2Cu phase. The sample exhibits high mechanical properties and does not require additional mold injection casting procedure to obtain fine microstructure. [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]

The structure of an arc-melted ingot of Ti 70 Fe 15 Co 15 alloy has been studied by X-ray diffractometry and scanning electron microscopy. Its microstructure consists of a primary P m m Ti(Fe, Co) phase and a binary Ti(Fe, Co) + I m m β-Ti solid solution eutectic. The mechanical properties were tested by an Instron-type machine. A sample cut from the central part of the ingot exhibits excellent mechanical properties. [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]

Abstract: The Mg-3.5Zn-0.6Gd (at. %) alloy was prepared and homogenized at 673K for 8h, and then extruded at 523K with an extrusion ratio of 9:1. The microstructure and mechanical properties of the extruded alloy have been investigated. Icosahedral quasicrystalline phase (I-phase) existed in extruded Mg–Zn–Gd-based alloys in two morphologies: (1) micron-scale I-phase formed in the solidification, (2) nano-scale ellipsoid-shape I-phase particles precipitated in the extrusion process. A definite orientation relationship and good atomic match between I-phase and α-Mg matrix were directly observed by conventional and high-resolution transmission electron microscopy (HRTEM), which contribute to the high tensile strength of 308MPa and the large plasticity of 16.4%. [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]

Liquid metal dealloying is a new process that can be applied to synthesize non-noble porous materials by preventing oxidation in a utilized metallic melt. The effect of dealloying rate was investigated by electron backscattered diffraction at the reaction layer at various temperatures (600–800 °C) using (FeCo) x Ni 100− x precursors in a Mg melt. FeCo ligaments transformed via different mechanisms depending on dealloying rate, temperature, and concentration of Ni. At the initial stage near the precursor surface, random texture was dominant in all cases. When the dealloying rate slowed down at 600 °C and 800 °C, the parent face-centered cubic grain structure played a significant role. The second stage differed depending on the dealloying conditions, including formation of <111>//normal direction fiber texture or an unknown specific orientation relationship. The orientation relationships also differed in the third stage. At 800 °C, the dealloying rate should be much slower than that at 600 °C to appear the third stage of the specific orientation relationship. • Dealloying rate strongly influences transformation mechanism in liquid metal dealloying. • When the dealloying rate is very high, random texture normally develops. • Ni70 showed a larger extended first stage of random texture than Ni30 and Ni50. • Governing orientation relationship depended on dealloying rate of Ni50 at 600 °C. • At 800 °C, fiber texture altered to an orientation relationship when dealloying rate decreased. [ABSTRACT FROM AUTHOR]

Liquid metal dealloying (LMD) is a promising technique that can be used to synthesize non-noble porous materials by preventing oxidation through using a metallic melt. However, the phase transformation behavior between a parent grain and synthesized ligaments surrounded by penetrating liquid metal channels remains unknown, despite its importance on the final physical properties. In this study, the temperature effect on the transformation mechanisms during the LMD process is investigated. At a low temperature of 600 °C, a fcc grain of (FeCo) x Ni 100− x precursors transforms to bcc FeCo ligaments by following unique orientation relationships (ORs), which differ from the well-known ORs like Bain, Kurdjumov-Sachs and Nishiyama-Wassermann. A few select variants are generated in the proposed ORs, and the formation of coincident site lattice boundaries is shown to play a crucial role in the variant selection to reduce the internal energy of the initial nanostructure. However, at a higher temperature of 800 °C, the crystal orientation of ligaments prefers to align in the <111> direction, which is parallel to the flow direction of Mg melt, owing to a strong interaction between the melt and ligaments. Ligaments are elongated along with the fiber texture, and this transformation behavior is irrelevant to the parent orientation. Image 1 • Governing orientation relationships during liquid metal dealloying were revealed. • Transformation mechanism varied depending on the dealloying temperature. • At 600 °C, the suggested ORs are rotated by 35.3°, 40.5°, and 45.1° from the KS OR. • Only a few variants were transformed from one parent fcc grain to bcc ligaments. • The formation of CSL boundaries play a crucial role in the variant selection. [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.

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]

The transition behavior from a Ti-Cu alloy to nanoporous α-Ti, the kinetics of the dealloying reaction, and the coarsening of nanoporous α-Ti were studied, and the mechanism of dealloying with a metallic melt was investigated. When a Ti50Cu50 alloy disk was immersed in a Mg melt, the Cu content decreased from the surface of the disk, and transition layers of α-Ti and Ti2Cu were formed. The growth of the transition layers followed a parabolic law and the activation energy was close to those reported for the diffusion of solute atoms in liquids, suggesting that diffusion of Cu in the Mg melt mainly contributed to the rate-controlling process for the dealloying reaction. The temperature and time dependences of the ligament size followed a power law with an exponent of 4, suggesting that surface diffusion plays an important role in coarsening. All of these results are consistent with those reported for dealloying in aqueous solution, indicating that the underlying dealloying mechanism in a metallic melt is similar to that in aqueous solution. [ABSTRACT FROM AUTHOR]

Three-dimensional interconnected nanoporous FeCo can be prepared by liquid metal dealloying. This study investigates the surface morphology and ordering kinetics of three-dimensional interconnected nanoporous FeCo. The chemical composition and dealloying temperature mutually influence the surface structure of the ligament scaffold. The ordering kinetics are accelerated by the surface-diffusion-driven coarsening in the nanoporous structure. Post-heat treatment leads to the development of precise nanofacets via the preferential growth of surface planes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Porous Ni- and Be-free Ti-based (Ti 45 Zr 10 Cu 31 Pd 10 Sn 4) bulk metallic glass (BMG) with a diameter exceeding 15 mm was developed by spark plasma sintering (SPS) the mixture of gas-atomized Ti-based glassy alloy powder and solid salt (NaCl) powder, followed by leaching treatment to eliminate the salt phase. The thermal and structural stability, microstructure, mechanical properties, corrosion behavior, and biocompatibility of the developed porous Ti-based BMG samples were investigated systematically. The developed porous Ti-based BMG alloy exhibited three times higher yield strength than that of the natural bone, simultaneously matched the Young's modulus of natural bone, and demonstrated high corrosion resistance and excellent biocompatibility. These results suggest that porous Ti-based BMGs produced by the SPS process open an advanced alternative for clinical applications under load-bearing conditions such as surgical implants. Highlights • Porous Ti-based bulk metallic glasses were developed by spark plasma sintering. • Porous Ti-based BMGs exhibited high strength and matched Young's modulus of natural bone. • Porous Ti-based BMGs demonstrated high corrosion resistance and excellent biocompatibility. [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]

Low ductility of glassy alloys prevents their technical application as structural materials. In this work, we study the Cu-based crystal-glassy composite material with good mechanical properties. Formation of the Cu[sub 10]Zr[sub 7] phase in the glassy matrix of a high-strength Cu[sub 50]Zr[sub 30]Ti[sub 10]Nb[sub 10] bulk alloy upon solidification led to higher Young’s modulus and enhanced ductility of such a composite compared to Cu-based glassy alloys. The as-cast structure was studied by x-ray diffraction and scanning electron microscopy. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Joining of Mg alloy to steel has received wide attention for design of multi-materials. This letter describes joining of immiscible pure iron and pure magnesium (Fe–Mg), as a simplified model, performed by solid metal dealloying (SMD) between Mg and Fe 100− x Ni x interlayers that were preliminary joined to the Fe part by diffusion bonding. SMD formed an Fe–Mg bicontinuous composite with interconnected morphology at the Fe–Mg weld interface. The effect of Ni composition x in the interlayer on the weld strength was examined. Strong joints were obtained when 30 < x < 50 at.%, which caused Mg base-metal fracture due to a well-interconnected Fe–Mg structure. When too little (x < 30 at.%) or too much (x > 60 at.%) Ni was added, interfacial fracture occurred due to limited dealloying reaction and formation of an isolated Fe product surrounded by a large amount of brittle Mg 2 Ni. [Display omitted] [ABSTRACT FROM AUTHOR]

A hierarchical porous metal has been prepared by two-step liquid metal dealloying using an alloy precursor containing two soluble components and two metal baths. After the first dealloying step, one of the soluble components is dissolved and a coarse porous structure is formed. After a shorter dealloying step in another melt, the other soluble component is dissolved and a fine porous structure is formed within the previously formed coarse ligaments. The resultant porous metal presents a hierarchical morphology with a bimodal pore distribution, resulting in a higher porosity and surface-area-to-volume ratio than what can be formed by one-step dealloying methods. [ABSTRACT FROM AUTHOR]

Porous NiTi shape-memory-alloy particle-reinforced Mg-based bulk metallic glass matrix composites were prepared by an ex-situ method. The composites show a larger plastic strain, higher fracture strength and obvious work-hardening behavior compared with their monolithic glassy counterparts. The ex-situ porous NiTi particles hinder the rapid propagation of shear bands, which generates multiplied shear bands, like other ductile metal particles, and undergo a stress-induced martensitic transformation, which is unique and contributes to work hardening. Local regions within one porous particle satisfy the optimal conditions of bulk metallic glass matrix composite structure, i.e., the average particle size and mean inter-particle spacing are close to the processing zone size, and thereby further improve the plasticity by localized plastic deformation. [ABSTRACT FROM AUTHOR]

The relatively low density of Ti (4.5 Mg/m3) implies high strength/density ratio for Ti-based alloys. A composite Ti65Fe35 alloy produced in the shape of arc-melted ingot of about 20 mm in diameter and 10 mm in height exhibits a high mechanical strength of 2.2 GPa at 6.7% ductility and a Young’s modulus of 149 GPa. Its microstructure consists of the cubic TiFe phase and a supersaturated BCC β-Ti solid solution. The formation of a supersaturated β-Ti solid solution and the disperse eutectic structure obtained result in a high strength of the Ti–Fe alloy which in addition to that has much higher ductility compared to that of nanostructured and glassy alloys. The Ti–Fe alloy is characterized by low cost of the alloying elements and does not require an additional injection mould casting procedure. [Copyright &y& Elsevier]

The solid dealloying reaction was investigated using (Fe,Cr)-Ni and Mg diffusion couples. Ni selectively reacted with Mg and the remaining Fe and Cr formed various topologies. An etching treatment provided interconnected Fe–Cr alloy with a ligament width below 200 nm, which is about one order of magnitude finer than that obtained for dealloying with Mg melt. The formation of ordered single-crystal nanofilaments at the dealloying front suggests that the topology evolved via the recently proposed interfacial spinodal decomposition and diffusion-coupled growth mechanism. [ABSTRACT FROM AUTHOR]

Silicon is a promising material for negative electrode in Li-ion batteries because of high gravimetric capacity. A Si nanomaterial that can accommodate volume expansion accompanied by lithiation is needed for practical application in Li-ion batteries. We prepare three-dimensional nanoporous interconnected silicon material with controlled pore and ligament sizes by dealloying using an Mg–Si precursor and Bi melt. The Mg atoms in the precursor selectively dissolve into Bi, and the remaining Si atoms self-organize into a nanoporous structure with characteristic length ranging from several ten to hundred nanometer. The Li-ion battery electrodes made from nanoporous silicon exhibit higher capacities, increased cycle lives, and improved rate performances compared with those made from commercial Si nanoparticles. Measurements on the electrical resistivity and electrode thickness change by lithiation/delithiation suggest that the superior performance of nanoporous Si electrode originates from the following: (1) The nanoporous Si has much lower electrical resistivity compared with that of the nanoparticle Si owing to the n-type dopant incorporated during dealloying. (2) The nanoporous Si-based electrode has higher porosity owing to the presence of intra-particle pores, which can accommodate Si expansion up to higher levels of lithiation. [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]

Gradient structure can achieve excellent mechanical properties in metallic materials through synergistic effects from heterogeneity. Conventional surface heterostructuring typically develops one single coupling gradient (i.e., hard surface and soft core). In this study, we present a novel approach to attain a dual-gradient structure, characterized by a series of hard surface-soft middle-hard core, through simple laser-scanning on cold-rolled metastable metallic materials. The resultant dual-gradient structure with significant synergistic strengthening improves the yield strength by more than two-fold compared to its annealed counterparts. Notably, the significant improvement in yield strength does not sacrifice ductility due to the unique deformation behavior of the dynamic-spreading phase transformation. The designed dual-gradient structure induces spatial-distinct phase stability along the depth, enabling to spreading phase transformation from the surface to the center during deformation. The inward-propagating phase transformation contributes to sustaining the heterostructure and the transformation-induced plasticity effect over a wide stress range while detouring stress concentration. Our study suggests a promising process design for fabricating a dual-gradient structure that possesses inward-spreading phase transformation to enhance the mechanical properties of heterostructured materials without compromising their ductility. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • We discovered liquid metal dealloying induced by eutectic melting. • Ti and Mg mechanically joined via bicontinuous microstructure formed by dealloying. • We clarified the joining conditions that interfacial strength exceeded the strength of pure Mg. Ti and Mg alloys, which have thermodynamically immiscible main components, have been chemically joined in previous work using a third element with high affinity for both elements. However, this strategy is challenging in precisely controlling brittle intermetallic compounds formed at a joint interface. In this study, we mechanically joined pure Ti and pure Mg without brittle layers by forming bicontinuous microstructure, 3D entanglement of immiscible phases, at the joint interface. We butt-joined pure Mg and Ti–Cu alloy interlayer, which we pre-diffusion bonded to the pure Ti and heated at 813 K and 20 MPa for 5 min. At the joint interface, Cu and Mg eutectic melted, which induced liquid metal dealloying of the interlayer. The entire Ti–Cu interlayer is dealloyed, and a byproduct (Mg–Cu phase) is removed by pressurization during melting. These brittle layer removal processes left only α-Ti/Mg–Cu phase bicontinuous microstructure at the joint interface, improving the joint strength. Ti/Mg joints fractured at the Mg base metal at ca. 90 MPa by tensile tests. The findings of this study provide the basis for achieving immiscible alloy joining, for which effective joining methods have not yet been established. [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]

Nanoporous non-noble metals with attractive properties can be fabricated by liquid metal dealloying (LMD). However, further refinement of the ligament size of nanoporous metals produced by LMD is desired because this high-temperature process induces rapid ligament coarsening. Herein, we fabricate nanoporous refractory metals and alloys by LMD. The molybdenum (Mo)-tantalum (Ta) alloy with the smallest ligament size of the specimens contains a B2 ordered structure, whereas the other specimens possess disordered structures. It is proposed that the B2 ordering of the Mo-Ta alloy suppresses ligament coarsening by restricting the surface diffusion of atoms during LMD. The Mo-Ta alloy with B2 ordered structure exists in a previously inaccessible low-temperature region of the related phase diagram, illustrating that LMD can enable access to new materials. Our results indicate that materials with refined ligaments may be obtained by LMD promoting the formation of ordered structures. [Display omitted] [ABSTRACT FROM AUTHOR]