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• Microstructure of the alloys is more sensitive to Nb rather than Ta. A slight difference in Nb content will affect the morphology of martensite and even induce ω phase transformation, resulting in completely different mechanical responses of the alloy. • The as-cast Ti-3Nb-13Ta-2Zr alloy shows the highest compressive strength (227 ±10 MPa), and compressive strain (74.3% ± 0.4%). • Nb and Ta content strongly affects Young's modulus and tensile properties of the alloys after rolling. The as-rolled Ti-3Nb-13Ta-2Zr alloy exhibits much lower modulus due to lower Nb content as well as more α"-martensite and β-phase, and a good combination of low modulus and high strength among all the designed alloys. Biomedical β-phase Ti-Nb-Ta-Zr alloys usually exhibit low elastic modulus with inadequate strength. In the present work, a series of newly developed dual-phase Ti- x Nb- y Ta-2Zr (wt.%) alloys with high performance were investigated in which the stability of β-phase was reduced under the guidelines of ab initio calculations and d-electronic theory. The effects of Nb and Ta contents on the microstructure, compressive and tensile properties were investigated. Results demonstrate that the designed Ti- x Nb- y Ta-2Zr alloys exhibit typical characteristics of α+β dual-phase microstructure. The microstructure of the alloys is more sensitive to Nb rather than Ta. The as-cast alloys exhibit needle-like α′ martensite at a lower Nb content of 3 wt.% and lamellar α′ martensite at an Nb content of 5 wt.%. Among the alloys, the Ti-3Nb-13Ta-2Zr alloy shows the highest compressive strength (2270 ± 10 MPa) and compressive strain (74.3% ± 0.4%). This superior performance is due to the combination of α+β dual-phase microstructure and stress-induced α" martensite. Besides, lattice distortion caused by Ta element also contributes to the compressive properties. Nb and Ta contents of the alloys strongly affect Young's modulus and tensile properties after rolling. The as-rolled Ti-3Nb-13Ta-2Zr alloy exhibits much lower modulus due to lower Nb content as well as more α" martensite and β phase with a good combination of low modulus and high strength among all the designed alloys. Atom probe tomography analysis reveals the element partitioning between the α and β phases in which Ta concentration is higher than Nb in the α phase. Also, the concentration of Ta is lower than that of Nb in the β phase, indicating that the β-stability of Nb is higher than that of Ta. This work proposes modern α+β dual-phase Ti- x Nb- y Ta-2Zr alloys as a new concept to design novel biomedical Ti alloys with high performance. [ABSTRACT FROM AUTHOR]

• High entropy alloy was strengthened by cryo-pre-straining-induced defects. • Strengthening mechanism was quantitatively revealed by neutron diffraction method. • Selective recovery of crystal defects assist to optimize the mechanical performance. Owing to their attractive structure and mechanical properties, high-entropy alloys (HEAs) and medium-entropy alloys (MEAs) have attracted considerable research interest. The strength of HEAs/MEAs with a single face-centered cubic (FCC) phase, on the other hand, requires improvement. Therefore, in this study, we demonstrate a strategy for increasing the room-temperature strength of FCC-phase HEAs/MEAs by tuning cryo-pre-straining-induced crystal defects via the temperature-dependent stacking fault energy-regulated plasticity mechanism. Through neutron diffraction line profile analysis and electron microscope observation, the effect of the tuned defects on the tensile strength was clarified. Due to the cryo-rolling-induced high dislocation density, mechanical twins, and stacking faults, the room-temperature yield strength of an equiatomic CoCrFeNi HEA was increased by ∼290%, from 243 MPa (as-recrystallized) to 941.6 MPa (30% cryo-rolled), while maintaining a tensile elongation of 18%. After partial recovery via heat treatment, the yield strength and ultimate tensile strength decreased slightly to 869 and 936 MPa, respectively. Conversely, the elongation increased to 25.6%. The dislocation density and distribution of the dislocations were found to contribute to the strengthening caused by forest dislocations, which warrants further investigation. This study discussed the possibility of developing single-phase high-performance HEAs by tuning pre-straining-induced crystal defects. [ABSTRACT FROM AUTHOR]

Sodium superionic conductors (NASICON) are pivotal for the functionality and safety of solid-state sodium batteries. Their mechanical properties and ionic conductivity are key performance metrics, yet their correlation remains inadequately understood. Addressing this gap is vital for concurrent enhancements in both properties. This study summarizes recent literature on the sintered polycrystalline NASICON solid electrolyte Na1+xZr2SixP3-xO12(NZSP, 0≤x ≤ 3), focusing on its mechanical properties and ionic conductivity, and identifies a positive correlation between these properties at ambient temperatures. Microstructural analysis reveals that a range of factors, including relative density, grain size, secondary phases, and crystal structures significantly influence the properties of NZSP. Notably, an increase in relative density uniquely contributes to simultaneous enhancements in both hardness and ionic conductivity. Consequently, future research should prioritize enhancing the relative density of NZSP, potentially by employing advanced sintering techniques such as spark plasma sintering (SPS) and microwave-assisted sintering. The correlation between mechanical properties and ionic conductivity observed in NZSP is also evident in other oxide solid electrolytes, such as garnet Li7La3Zr2O12(LLZO). This investigation not only suggests a potential linkage between these crucial properties but also guides subsequent strategies for refining polycrystalline oxide solid electrolytes for advanced battery technologies.

• The power-law relationship between creep rate decay and time of high-entropy metallic glass can be well described in the framework of shear transformation zones. • Physical aging below the glass transition temperature reduces the number of initial shear transformation zones which contribute to creep. • Cyclic loading can tailor the "forward" jump operations competing with the "backward" ones of shear transformation zones by controlling the recovery time. The power-law relationship between creep rate decay and time is one of the intrinsic characteristics of metallic glasses. In the current work, a La 30 Ce 30 Ni 10 Al 20 Co 10 high-entropy metallic glass was selected as the model alloy to test the influences of physical aging and cyclic loading on the power-law creep mechanism, which was probed by the dynamic mechanical analysis in terms of the stochastic activation, and contiguous interplay and permeation of shear transformation zones. It is demonstrated that a notable discrepancy appears between thermal treatment and mechanical treatment on the power-law creep mechanism of this high-entropy metallic glass. On the one hand, physical aging below the glass transition temperature introduces the annihilation of potential shear transformation zones which contribute to creep. On the other hand, cyclic loading can tailor the "forward" jump operations competing with the "backward" ones of shear transformation zones by controlling the interval time (recovery time). The current research offers a new pathway towards understanding the creep mechanism of high-entropy metallic glasses. [Display omitted] [ABSTRACT FROM AUTHOR]

Relaxation dynamics, essential for the structural evolution of non-equilibrium systems like glassy materials, remain enigmatic. Here, we explore relaxation dynamics and viscoelastic properties in three types of metallic glasses with distinct β relaxation behavior. In systems with significant β relaxation, stress relaxation and creep experiments reveal a transition from two-step to one-step relaxation with rising temperature. However, such a phenomenon is absent in systems with weaker β relaxation. We model the two-step relaxation process using a double Kohlrausch-Williams-Watts equation, and the obtained relaxation times elegantly adhere to the Arrhenius relationship. By combining fitted activation energies with theoretical analysis, we conclusively attribute these relaxation processes to β relaxation and α relaxation, respectively. Finally, we analyze the relaxation time spectra of two processes and establish a comprehensive picture linking dynamic relaxation with viscoelasticity. Our study provides new strategies for probing the complex relaxation behaviors of glasses from the perspective of viscoelasticity.

The spark plug is one of the important components in the gasoline engine's combustion chamber. To reduce vehicle emissions, the platinum spark plug is selected due to its good performance. Due to the high productivity of resistance spot welding (RSW), a micro-scale RSW process is employed to assemble the platinum tip to Inconel600 part in the production of spark plugs. In order to understand the electric-thermal-mechanics phenomena during micro resistance spot welding spark plug for controlling the welding quality and saving electric energy, a three-dimensional simulation model and the in-house finite element program JWRIAN-RSW3D were developed. The potential history and upper electrode displacement results were verified with experiments. Numerical case studies were made to investigate the influence magnitude of welding current on the electric-thermal-mechanics phenomena. The developed model reveals inside phenomena to clearly understand the welding mechanism for potential, current density, temperature, electrode displacement and their distribution/history as well as the molten zone. The comprehensive phenomena of maximum temperature distribution on both base metals and Inconel600 were clarified using a top perspective, revealing differences in distribution on the contact surface between horizontal and vertical sections. To achieve a complete welding joint, the molten zone on the contact area is required carefully in order to facilitate the bonding of both base metals. Based on simulation results for three welding conditions, the alternating current at the magnitude of 1.2 kA with the welding time of 0.1 s is recommended to obtain the welded joint with minimized energy consumption in production.

Phase morphology and the distribution of the strengthening phase generally have a strong influence on the movement of dislocations. The presence of minor alloying element Mg in Cu–30Fe alloy significantly affects both the morphology and distribution of the strengthening phase. Dendritic α-Fe is transformed into a spherical morphology because of changes in the chemical composition during the solidification process. The presence of Mg leads to the formation of secondary phase-separated Cu within the α-Fe phase and to increasing heterogeneity of the gradient size of the α-Fe phase. The increased volume fraction of α-Fe enhanced by secondary separated Cu, refinement of α-Fe, and the degree of distribution enhanced the yield strength of this alloy by 40% compared with that of Cu–30Fe. This result can be used as a guide to modifying the morphology of Cu–Fe alloys and improve understanding of strengthening mechanism of this system.

Nanostructured silicon with its high theoretical capacity and ability to accommodate volume expansion has attracted great attention as a promising anode material for Lithium ion (Li-ion) batteries. Liquid metal dealloying method, is a novel method to create nanoporous silicon (np-Si). The assembled Li-ion batteries based on such np-Si anode can be cycled beyond 1500 cycles, in 1000 mA h/g constant capacity cycling mode with consistent performance; however, it suffers from degradation after ~ 460 cycles, while being cycled under 2000 mA h/g. To reveal the failure mechanism and differences in the morphological evolution in different capacity cycling modes in the np-Si anode, we conducted synchrotron X-ray nano-tomography studies. The three dimensional (3D) morphological evolution was visualized and quantified as a function of the number of cycles and cycling capacities. By comparing the 3D morphology under each cycling condition and correlating these 3D morphological changes with cycling-life performance, we elucidate the failure mechanism of the np-Si electrodes resulting from a mesoscopic to macroscopic deformation, involving volume expansion and gradual delamination. In particular, the shorter cycling life in higher-capacity cycling mode stems from particle agglomeration. Overall, while the nanoporous structure can accommodate the volume expansion locally, these mesoscopic and macroscopic deformations ultimately result in heterogeneous stress distribution with faster delamination. The work thus sheds the light on the importance to consider the structural evolution at the mesoscopic and macroscopic scales, while designing nano-structured energy storage materials for enhanced performances, particularly for long cycling-life durability.

Nanoporous materials, especially those fabricated by liquid metal dealloying processes, possess great potential in a wide range of applications due to their high surface area, bicontinuous structure with both open pores for transport and solid phase for conductivity or support, and low material cost. Here, we used X-ray nanotomography and X-ray fluorescence microscopy to reveal the three-dimensional (3D) morphology and elemental distribution within materials. Focusing on nanoporous stainless steel, we evaluated the 3D morphology of the dealloying front and established a quantitative processing–structure–property relationship at a later stage of dealloying. The morphological differences of samples created by liquid metal dealloying and aqueous dealloying methods were also discussed. We concluded that it is particularly important to consider the dealloying, coarsening, and densification mechanisms in influencing the performance-determining, critical 3D parameters, such as tortuosity, pore size, porosity, curvature, and interfacial shape.

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

To clarify microscopic elastic properties of a Pd40Ni40P20 bulk metallic glass, inelastic X-ray scattering (IXS) experiments were carried out using high-resolution IXS spectrometer installed at BL35XU/SPring-8. Clear longitudinal acoustic (LA) excitation modes are observed in the whole momentum transfer Q range up to ~22 nm-1. The microscopic sound velocity of the LA modes obtained from the Q → 0 limit of the dispersion relation is about 12% faster than the macroscopic value, suggesting the microscopic heterogeneity in the elastic properties of this BMG. In addition, transverse acoustic (TA) modes can be deduced from a detailed analysis of the IXS spectra. The microscopic Poisson’s ratio obtained from the ratio of the excitation energies of the TA and LA modes is 0.47 ± 0.04, larger than the macroscopic value of 0.40. Thus, the fragile nature of this BMG already found in the macroscopic sense is much enhanced in the microscopic view.

Abstract

Amorphous Cu–Zr metallic alloys were studied as precursors to catalysts for methanol steam reforming to produce hydrogen. The alloy ribbons were prepared by single-roll rapid solidification, and the optimum pretreatment method and conditions were determined. The activity of the catalysts prepared by the improved pretreatment method was greater than that of previously prepared catalysts by two degrees of magnitude. The addition of a very small amount of Pt enhanced the activity without increasing CO formation.

Anomalous X-ray scattering experiments were performed on Zr63Ni25Al12bulk metallic glass. The results were analyzed using reverse Monte Carlo modeling to obtain local- and intermediate-range atomic configurations of this good metallic glass former. Although the Al-related partial information is not reliable due to the small values of their weighting factors in X-ray scattering, good partial information could be obtained from a reverse Monte Carlo analysis. The obtained structural information is given by parameters such as bond angle distributions, bond orientation order parameters, the Warren–Cowley order parameters, and Voronoi polyhedra. Results are compared to the previous results from Fukunaga et al. using X-ray and neutron total scattering.

We Successfully Prepared the Rod Glassy Samples of (Fe1-xCox)76Si9B10P5 (x = 0~0.4) Bulk Metallic Glass (BMG) with the Diameters up to 3.0 mm by Substituting Fe for a Small Amount of Co Element. A Certain Amount of Co Substitution for Fe Contributes to the Increase of the Glass-Forming Ability (GFA) while Maintaining Good Mechanical Properties (the Fracture Strength up to 3700 MPa). This Co-Added Ferromagnetic Bulk Glassy Alloy System Also Exhibits a Higher Saturation Magnetization of 1.49 T and Lower Coercive Force (Hc, 1.2 A/m). The Fe-Based BMGs with Alloying a Small Amount of Co Element Demonstrate Excellent Combination of High GFA, Good Soft-Magnetic Properties as Well as High Strength.

In this study, rapidly solidified Co-Sn-Ti and Co-Sn-Si alloys were investigated as candidate cathodic materials for lithium-ion batteries. (Co0.5Sn0.5)1-xTix (x=0.1, 0.2, 0.3, 0.4) and (Co0.5Sn0.5)0.9Si0.1 alloys were produced by Ar arc-melting. These alloys were further rapidly solidified into ribbons by the single-roll melt-spinning method. Constituent phases in the ribbons were identified by XRD, indicating that all of the alloys were composed of crystalline multi-phases with no amorphous phase. The microstructure of the ribbons was observed by SEM and TEM, and the chemical composition of constituent phases was analyzed by TEM-EDS. It is found from the SEM and TEM observations that the grain size of the constituent phases ranged from tens to hundreds nanometers due to the rapid solidification effect.

A Zr65Al7.5Ni10Cu17.5-xPdx (x=0-17.5 at. %) alloy system is found to exhibit a different dependence of glass-forming ability (GFA) on atmosphere-pressure during mold casting process. High-Pd alloys (x=7.5-17.5) show a remarkable increase of critical size for glass formation (dc) as casting-atmosphere (Ar) pressure varies from vacuum to ambient. No significant change of dc, however, is observed in low-Pd alloys (x=0-5) despite the variation in atmosphere pressure. The origin of the phenomenon is unveiled by correlating the cooling characteristic during mold casting and on-cooling phase transformation characteristic of the alloy system.

Monolithic Zr65Al7.5Ni10Pd17.5 and Zr65Al7.5Ni10Cu17.5 hardly had plastic deformability in tension at room temperature, although Zr65Al7.5Ni10Pd17.5 showed a large plastic strain in compression. A depressed zone that is the evidence of viscous flow deformation (so-called viscous flow depression zone; VFD-zone) was observed for Zr65Al7.5Ni10Pd17.5 around the edge at the point of failure on its specimen surfaces. However, no VFD-zone was seen for Zr65Al7.5Ni10Cu17.5. Thus, a clear difference in tensile plastic behavior was found between Zr65Al7.5Ni10Pd17.5 and Zr65Al7.5Ni10Cu17.5. A structural change in the vicinity of the fracture surface of Zr65Al7.5Ni10Pd17.5 was measured by micro-beam X-ray diffractometry (MB-XRD). We may be able to discuss the room temperature plasticity of Zr65Al7.5Ni10Cu17.5-xPdx bulk metallic glasses correlating with the phase stability of the amorphous and icosahedral quasi-crystalline phases.

Crystalline precipitates in a bulk-metallic-glass (BMG) braze were investigated with an intense x-ray microbeam. The precipitates were found in the Pd40Cu30P20Ni10 BMG braze matrix after joining crystalline Ti-6Al-7Nb. However, the role (if any) played by the precipitates in improving the mechanical bond of the BMG/crystalline joint is unknown. X-ray microdiffraction and microfluorescence measurements from small sample volumes were made with an ~ 0.5 x 0.5 μm2 beam. Spatially-resolved Laue diffraction and x-ray fluorescence measurements were made on several second-phase crystals within the BMG matrix. Although precipitate crystals with the observed compositions were anticipated to be predominantly hexagonal, one of the crystals was found to be cubic or tetragonal. The instrumentation includes capabilities for 3D depth-resolved measurements of crystal structure and for fluorescence analysis of elemental composition. Depth profiling gave information about the grain distribution and morphology in the BMG matrix.

The hydrogen-induced internal friction and mechanical strength of the Ti-rich Ti34Zr11Cu47Ni8 and (Ti34Zr11Cu47Ni8)98Si2 hydrogenated glassy alloys have been investigated. It is found that the tensile strength is more than 0.8 GPa at room temperature when the hydrogen content is below about 20 at% for both alloys. The frequency dependence of peak temperature of the hydrogen-induced internal friction of (Ti34Zr11Cu47Ni8)98Si2-17.3 at%H hydrogenated glassy alloys has been clarified. Activation energy and pre-exponential factor are estimated to be 0.35 eV and 1.3x10-12, respectively. Compared with these values with those of Zr40Cu49Al10Si1 hydrogenated glassy alloys which show an internal friction peak around 300 K at about 300 Hz, it is found that the activation energy is much smaller than that of the latter although the pre-exponential factor is almost the same. Considering their similar composition and different component (Al), it is suggested that the component Al of the latter glassy alloys is effective for the higher activation energy which results in the increase of the peak temperature.

Mg-8Zn-4Al-xY base alloys containing an icosahedral quasicrystal phase (i-phase) as a main strengthening phase were prepared by casting into a copper mould at moderate cooling rates. The Y addition was effective for decreasing the size of i-phase and the more homogeneousness of its dispersed state. The mechanical properties at room temperature were much superior to those of AZ91 alloy. The creep tests indicated a promising high temperature creep resistance of the quasicrystal-reinforced Mg-Zn-Al-Y cast alloy. The dislocation characteristic in crept specimens which containing i-phase and no i-phase was analyzed and strengthening mechanism was discussed.

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Liquid metal dealloying (LMD) has recently attracted significant attention. Because the LMD process enables the production of three-dimensional (3D) interconnected non-noble metallic materials. In addition, the metallic melt medium is useful for the development of heterostructure (HS) metal-metal composites. However, the solidified liquid metal phase (low melting point metals such as Mg, Bi, Sn, or Cu) has a much lower strength than the developed ligament phase (e.g., Fe, FeCr, Ti, etc.). In this study, the soft Mg phase was strengthened by adding alloying element of Ni. A eutectic composition of Mg-10at.%Ni melt leads to the formation of fine eutectic structure of (Mg-Mg2Ni) within 3D interconnected morphology. This hierarchical heterostructured composite consisted of FeCr ligament and Mg-Mg2Ni lamellar, and a high yield strength of 280 MPa and a noticeable elongation (1.5%) were achieved. The complex 3D morphology of ligament and lamellar geometrically constraint each other, and it prevents the early fracture of brittle Mg-Mg2Ni lamellar phase. The alloy design for the LMD melt gives insights for hierarchical HS materials with outstanding mechanical properties for structural applications.

Low modulus β-type Ti-35Nb-2Ta-3Zr alloy scaffold was fabricated by laser powder bed fusion (L-PBF). The complex microstructure and mechanical properties were characterized systematically. The martensitic interstitial complex transitions (ICTs) from β to α" (β→α"), α" to ω (α"─ω), and β to α" and ω (β→α─ω) phases are accompanied by dislocation pile-ups and twins in a heterogeneous manner. A homaloidal transition was observed with astraddle ω and α"Mnanolayers and partial nanolayers along the boundaries of the α"Tmartensitic twin. Crystallographic characterization confirmed that {332}〈113〉 and {112}〈111〉 twinning and shear stress assisted the α─ω and β→α" transitions at the interface of the β region. Both the αꞌꞌ martensitic twin and ω formation were observed adjacent to the {332}〈113〉 type twinning mode. The [332] twinning were instigated and nucleated through ω-phase formation. The secondary [112] twins amid the primary [332] twinning were instigated and nucleated through ω-phase formation. Multiple slip bands were identified on the surface of the micropillar after the microcompression testing. Moreover, high-density dislocations and dislocation pile-ups were found alongside the twins and grain boundaries. In addition, {112}〈111〉 twinning was identified amongst dislocation pile-ups. This work reveals a novel complex phase transformation that could play a significant role in applications such as biomedical implants.

Elastography, an imaging modality for mapping elastic modulus in soft viscoelastic materials, has been developed using magnetic resonance imaging and ultrasound imaging, but few studies were reported on using X-ray imaging. We report on dynamic X-ray elastography, which relies on shear-wave propagation. We pneumatically vibrated polyacrylamide gel phantoms and obtained two-dimensional maps of storage and loss moduli, which were determined from temporal variation in displacement vectors of the vibrating particles in the phantoms. Our experiment provided storage moduli with a precision of 30% and a spatial resolution was one order of magnitude higher than other imaging modalities.

Ti-B-Cu and Ti-C-Cu systems are interesting from the viewpoint of the development of ceramic particle-reinforced copper matrix composites. In this work, the phase and structural evolution upon the interaction of Ti33Cu67 and Ti25Cu75 alloys obtained by melt spinning with carbon or boron was studied. The reactions were carried out in the ball-milled mixtures subjected to Spark Plasma Sintering at 900 degC. The products of the reactions were composites containing TiC or TiB2 nanoparticles distributed in the copper matrix. The in-situ synthesized TiC and TiB2 nanoparticles were extremely fine (10-20 nm). The distribution pattern of the particles in the matrix was similar in the TiC-Cu and TiB2-Cu systems: composite regions were intermixed with copper regions free from the ceramic particles. It was shown that, when the Ti25Cu75 alloy was melted first by heating up to 900 degC and then forced to interact with carbon, TiC particles two orders of magnitude larger in size grew in the copper matrix.

Bulk metallic glasses—formed by supercooling the liquid state of certain metallic alloys—have potentially superior mechanical properties to crystalline materials. Here, we report a Co43Fe20Ta5.5B31.5glassy alloy exhibiting ultrahigh fracture strength of 5,185 MPa, high Young's modulus of 268 GPa, high specific strength of 6.0 × 105Nm kg−1and high specific Young's modulus of 31 × 106Nm kg−1. The strength, specific strength and specific Young's modulus are higher than previous values reported for any bulk crystalline or glassy alloys. Excellent formability is manifested by large tensile elongation of 1,400% and large reduction ratio in thickness above 90% in the supercooled liquid region. The ultrahigh-strength alloy also exhibited soft magnetic properties with extremely high permeability of 550,000. This alloy is promising as a new ultrahigh-strength material with good deformability and soft magnetic properties.

A high-aspect-ratio absorption grating with a pitch of several um is a key component of X-ray grating interferometery, which is an X-ray phase imaging technique that allows for highly sensitive X-ray imaging with a compact laboratory X-ray source. Here, we report that X-ray phase imaging was successfully performed at 15 keV by using a 23 +- 1-um-height, 9-um-pitch absorption grating (10 x 10 mm2) based on Gd (Gd60Cu25Al15) fabricated by a metallic glass imprinting technique. The imprinting technique is cost-efficient and has a high-production rate, and will be widely used for fabricating gratings not only for X-rays but also neutrons in the near future.

In X-ray grating interferometry, the fabrication of thick transmission gratings with pitches of several micrometers has been a key subject. We report on a metallic glass imprinting technique for fabricating an interferometer grating. We successfully fabricated an 8-µm-pitch, 10-µm-thick grating (26 mm2) made of Pd42.5Ni7.5Cu30P20metallic glass by using the technique, and as a demonstration we also performed X-ray phase imaging with the grating. The technique can be applied to fabricate not only X-ray but also neutron gratings potentially at high production rates and low costs and is expected to be widely used in the near future.

An imprint process of Pd-based metallic glass is used to create a high-aspect-ratio two-dimensional wire array structure for filtering terahertz (THz) radiation. By the simplified imprinting process, a 10×10 straight wire array with a wire height of ?320 µm and a diameter of 100.6 µm is produced. The negligibly small expansion of ?0.3% confirms the excellent thermal imprinting property of metallic glass. The periodic wire array is shown to act as a high-pass filter in the THz range, and the transmission property measurement reveals a turn-on frequency of 0.4 THz, suggesting the promising approach and material for robust high-pass filters.

Nonlinear viscoelastic behaviors of a Zr55Al10Ni5Cu30glassy alloy are investigated experimentally and by theoretical modeling, based on the hypothesis of stress-induced structural relaxation and the concept of fictive stress. The model calculation curves agree well quantitatively with the experimental results. Structural changes of the nonlinear viscoelasticity during complex-step tests are expressed directly by the fictive stress. In addition, the critical condition under which the transition from linear to nonlinear viscoelasticity occurs is clarified on the basis of this model.

A model, based on the hypothesis of stress-induced structural relaxation and a concept of fictive stress, is proposed for nonlinear viscoelastic behavior in glassy materials. A model calculation has been carried out on the stress-overshoot phenomenon observed in metallic glasses. The model calculation reproduces the experimental results of a Pd40Ni10Cu30P20glass fairly well, in particular, the development of stress-overshoot behavior with increasing strain rate and lowered temperature. In addition, the model reveals a stress-overshoot and -undershoot oscillatory behavior which has not been reported previously in metallic glasses, but has been observed in many polymer solutions.