Deformation behavior of thermally rejuvenated Zr-Cu-Al-(Ti) bulk metallic glass.

The deformation behavior of metallic glasses has been shown in prior studies to be often dependent on its structural state, namely higher energy "rejuvenated" state versus lower energy "relaxed" state. Here, the deformation behavior of thermally rejuvenated Zr-Cu-Al-(Ti) bulk metallic glasses (BMGs) was evaluated. Rejuvenation was achieved by cryogenic thermal cycling with increase of free volume measured in terms of enthalpy of relaxation. Hardness, stiffness, and yield strength of the BMGs were all found to decrease while plasticity increased after rejuvenation. More free volume in the rejuvenated BMG resulted in homogeneous plastic deformation as was evident from the high strain rate sensitivity and more pronounced shear band multiplication during uniaxial compression. Shear transformation zone (STZ) volume was calculated by cooperative shear model and correlated well with the change in structural state after rejuvenation. The enhanced plasticity with the addition of 1 at. % Ti as well as after cryogenic thermal cycling was explained by lower activation energy for shear flow initiation due to increased heterogeneity induced in the system. Molecular dynamics simulation demonstrated that the variation in plastic deformation behavior is correlated with local atomic structure changes.

Dissolution Manufacturing Strategy for the Facile Synthesis of Nanoporous Metallic Glass Multifunctional Catalyst.

The quest for heightened energy efficiency is inextricably linked to advancements in energy storage and conversion technologies, wherein multifunctional catalysts play a pivotal role by mitigating the slow kinetics endemic to many catalytic reactions. The intricate synthesis and bespoke design of such catalysts, however, present notable challenges. Addressing this, the present study capitalizes on a novel dissolution manufacturing strategy to engineer self-supporting, nanoporous multifunctional electrocatalysts, circumventing the prevalent issue of customizing catalytic functionalities upon demand. This innovative approach grants the flexibility to finely tune the incorporation of active species and metalloid binders, culminating in the creation of a self-supporting nanoporous metal glass electrocatalyst doped with RuO2 (NPMG@RuO2) with outstanding performance in alkaline media. The catalyst showcases superior electrocatalytic activity, achieving low overpotentials of 41.50 mV for the Hydrogen Evolution Reaction and 226.0 mV for Oxygen Evolution Reaction alongside sustained stability over 620 hours.These achievements are attributed to the distinct nanoporous architecture that ensures a high density of catalytic sites and mechanical strength, bolstered by the synergistic interplay between RuO2 and Pt-based metallic glass. The findings provide a versatile template for the development of nanoporous multifunctional catalysts, signifying a leap forward in the realm of energy conversion technologies.

Tensile Deformation Mechanism of an In Situ Formed Ti-Based Bulk Metallic Glass Composites.

Ti-based bulk metallic glass composites (BMGMCs) containing an in situ formed metastable ß phase normally exhibit enhanced plasticity attributed to induced phase transformation or twinning. However, the underlying deformation micromechanism remains controversial. This study investigates a novel deformation mechanism of Ti-based BMGMCs with a composition of Ti42.3Zr28Cu8.3Nb4.7Ni1.7Be15 (at%). The microstructures after tension were analyzed using advanced electron microscopy. The dendrites were homogeneously distributed in the glassy matrix with a volume fraction of 55 ± 2% and a size of 1~5 µm. The BMGMCs deformed in a serrated manner with a fracture strength (σf) of ~1710 MPa and a fracture strain of ~7.1%, accompanying strain hardening. The plastic deformation beyond yielding was achieved by a synergistic action, which includes shear banding, localized amorphization and a localized BCC (ß-Ti) to HCP (α-Ti) structural transition. The localized amorphization was caused by high local strain rates during shear band extension from the amorphous matrix to the crystalline reinforcements. The localized structural transition from BCC to HCP resulted from accumulating concentrated stress during deformation. The synergistic action enriches our understanding of the deformation mechanism of Ti-based BMGMCs and also sheds light on material design and performance improvement.

Investigation of Mechanical and Corrosion Properties of New Mg-Zn-Ga Amorphous Alloys for Biomedical Applications.

Magnesium alloys are considered as promising materials for use as biodegradable implants due to their biocompatibility and similarity to human bone properties. However, their high corrosion rate in bodily fluids limits their use. To address this issue, amorphization can be used to inhibit microgalvanic corrosion and increase corrosion resistance. The Mg-Zn-Ga metallic glass system was investigated in this study, which shows potential for improving the corrosion resistance of magnesium alloys for biodegradable implants. According to clinical tests, it has been demonstrated that Ga ions are effective in the regeneration of bone tissue. The microstructure, phase composition, and phase transition temperatures of sixteen Mg-Zn-Ga alloys were analyzed. In addition, a liquidus projection of the Mg-Zn-Ga system was constructed and validated through the thermodynamic calculations based on the CALPHAD-type database. Furthermore, amorphous ribbons were prepared by rapid solidification of the melt for prospective alloys. XRD and DSC analysis indicate that the alloys with the most potential possess an amorphous structure. The ribbons exhibit an ultimate tensile strength of up to 524 MPa and a low corrosion rate of 0.1-0.3 mm/year in Hanks' solution. Therefore, it appears that Mg-Zn-Ga metallic glass alloys could be suitable for biodegradable applications.

Atomic Structure Amorphization and Electronic Structure Reconstruction of FeCoNiCrMox High-Entropy Alloy Nanoparticles for Highly Efficient Water Oxidation.

The complexity of the multielement interaction in high-entropy alloys (HEAs) may provide more active sites to adapt different catalytic reaction steps in oxygen evolution reaction (OER). Investigating the correlation between structure and performance of HEAs electrocatalysts is both essential and challenging. In this work, FeCoNiCrMox HEA nanoparticles are successfully fabricated utilizing a unique nanofabrication method called inert gas condensation. With the increase of high-valence metal component Mo, the atomic structure amorphization and electronic structure reconstruction are unveiled. According to the X-ray photoelectron spectroscopy valence spectra, the d-band center of FeCoNiCrMox is ascending, and thus enhancing the adsorption energy. Synchrotron pair distribution function analysis reflects the degree of structural disorder and reveals a robust correlation with the intrinsic OER activities of the electrocatalysts. FeCoNiCrMo1.0 high-entropy metallic glass nanoparticles exhibit an outstanding OER performance with an ultralow overpotential of 294.5 mV at a high current density of 100 mA cm-2. This work brings fundamental and practical insights into the modulation mechanism of metal components of HEAs catalysts for developing OER.

Near-Field-Regulated Ultrafast Laser Supra-Wavelength Structuring Directly on Ultrahard Metallic Glasses.

The ultrafast-laser-matter interactions enable "top-down" laser surface structuring, especially for materials difficult to process, with "bottom-up" self-organizing features. The subwavelength scenarios of laser-induced structuring are improved in defects and long-range order by applying positive/negative feedbacks. It is still hardly reported for supra-wavelength laser structuring more associated with complicated thermo/hydro-dynamics. For the first time to the knowledge, the near-field-regulated ultrafast-laser lithography of self-arrayed supra-wavelength micro/nano-pores directly on ultra-hard metallic glass is developed here. The plasmonic hot spots on pre-structures, as the positive feedback, clamped the lateral geometries (i.e., position, size). Simultaneously, it drilled and self-organized into micro/nano-pore arrays by photo-dynamic plasma ablation and Marangoni removal confined under specific femtosecond-laser irradiation, as the negative feedback. The mechanisms and finite element modeling of the multi-physical transduction (based on the two-temperature model), the far-field/near-field coupling, and the polarization dependence during laser-matter interactions are studied. Large-area micro/nano-pore arrays (centimeter scale or larger)  are manufactured with tunable periods (1-5 µm) and geometries (e.g., diameters of 500 nm-6 µm using 343, 515, and 1030 lasers, respectively). Consequently, the mid/far-infrared reflectivity at 2.5-6.5 µm iss decreased from ≈80% to ≈5%. The universality of multi-physical coupling and near-field enhancements makes this approach widely applicable, or even irreplaceable, in various applications.

The Use of Polyimide as a Bonding Material to Improve the Mechanical Stability, Magnetic and Acoustic Properties of the Transformer Core Based on Amorphous Steel.

The constantly evolving electrification also entails an increase in requirements for the effective and efficient distribution of electricity with the lowest possible power losses. Such needs can be met by highly effective electrical devices, and one of them is a transformer whose main component is a magnetic core. Currently, one of the soft magnetic materials used alternatively for the production of transformer cores are amorphous metal strips with competitive losses. However, to successfully use these materials, a key problem must be solved: limited mechanical stability. The presented article describes the development and application of a polyimide-based binder for efficient bonding of an amorphous metal ribbon. The layered binder was characterized using confocal microscopy, scanning electron microscopy and Raman spectroscopy, and its anticorrosion and mechanical properties were examined. As a final step, a prototype of a toroidal magnetic core bonded with the binder was manufactured and subjected to the evaluation of no-load loss and the analysis of the emitted noise. It was confirmed that the proposed polyimide binder tremendously improved the mechanical stability while reducing core losses and audible noise.

Microstructure and Mechanical Properties of Multilayered Ti-Based Bulk Metallic Glass Composites Containing Various Thicknesses of Ti-Rich Laminates.

In order to optimize the balance between strength and toughness, a series of multilayered Ti-based bulk metallic glass composites (BMGCs) with varying thicknesses of Ti-rich layers were successfully fabricated. The findings reveal that with an increase in the thickness of the Ti-rich layers, both the flexural yield strength and ultimate strength decreased from 2066 MPa and 2717 MPa to 668 MPa and 1163 MPa, respectively. Conversely, there was a noticeable increase in flexural strain. The fracture toughness of these multilayered Ti-based BMGCs decreased as the thickness of the Ti-rich layers increased; nevertheless, it stabilized at approximately 80 MPa·m1/2 when the thickness reached 100 µm. It was observed that a shift in the dominant deformation mode may be accountable for this phenomenon. These noteworthy characteristics suggest that adjusting the thickness of Ti-rich layers in multilayered BMGCs can effectively optimize mechanical performance, shedding light on the manufacturing of novel BMGCs with high performance.

A Zn-Ca-Based Metallic Glass Composite Material for Rapid Degradation of Azo Dyes.

The catalytic capabilities of metals in degrading azo dyes have garnered extensive interest; however, selecting highly efficient metals remains a significant challenge. We have developed a Zn-Ca-based metallic glass composite which shows outstanding degradation efficiency for Direct Blue 6. This alloy comprises a Zn2Ca crystalline phase and an amorphous matrix, allowing for the degradation of azo dyes within minutes in a wide temperature range of 0-60 °C. Kinetic calculations reveal an exceptionally low activation energy of 8.99 kJ/mol. The rapid degradation is attributed to the active element Ca and the unique amorphous structure of the matrix, which not only facilitates abundant redox conditions but also minimizes the hydrolysis of the active element. The newly developed metallic glass composite exhibits a notably higher azo dye degradation rate compared to those of general metallic glasses, offering a new avenue for the rapid degradation of azo dyes. This paper holds significant importance for the development of novel azo dye wastewater treatment agents.

Recent Advances in and Challenges with Fe-Based Metallic Glasses for Catalytic Efficiency: Environment and Energy Fields.

Metallic glass is being gradually recognized for its unique disordered atomic configuration and excellent catalytic activity, so is of great significance in the field of catalysis. Recent reports have demonstrated that Fe-based metallic glass, as a competitive new catalyst, has good catalytic activity for the fields of environment and energy, including high catalytic efficiency and stability. This review introduces the latest developments in metallic glasses with various atomic components and their excellent catalytic properties as catalysts. In this article, the influence of Fe-based metallic glass catalysts on the catalytic activity of dye wastewater treatment and water-splitting is discussed. The catalytic performance in different atomic composition systems and different water environment systems, and the preparation parameters to improve the surface activity of catalysts, are reviewed. This review also describes several prospects in the future development and practical application of Fe-based metallic glass catalysts and provides a new reference for the synthesis of novel catalysts.

Multi-Scale Traditional and Non-Traditional Machining of Bulk Metallic Glasses (BMGs)-Review of Challenges, Recent Advances, and Future Directions.

Bulk metallic glasses (BMGs) are growing in popularity prominently due to their potential in micro-electromechanical systems (MEMSs) and aerospace applications. BMGs have unique mechanical properties, i.e., high strength, hardness, modulus of elasticity, and wear resistance, due to their disordered atomic structure. Due to their unique mechanical properties and amorphous structures, machining of BMGs remains a challenge. This paper aims to carry out a detailed literature review on various aspects of the machining of bulk metallic glasses using both conventional and non-conventional processes, including experimental approaches, modeling, statistical findings, challenges, and guidelines for machining this difficult-to-machine material. Conventional machining processes were found to be challenging for machining bulk metallic glasses due to their high hardness, brittleness, and tendency to convert their amorphous structure into a crystalline structure, especially at the machined surface and sub-surface. Although their high electrical conductivity makes them suitable for machining by non-conventional processes, they impose new challenges such as heat-affected zones and crystallization. Therefore, the successful machining of BMGs requires more in-depth analysis of cutting forces, tool wear, burr formation, surface finish, recast layers or heat-affected zones, crystallization, and mechanical property changes among different varieties of BMGs. This review paper provides guidelines emerging from in-depth analysis of previous studies, as well as offering directions for future research in the machining of BMGs.

Effect of Strain Rate on Mechanical Deformation Behavior in CuZr Metallic Glass.

Tensile tests were performed on Cu64Zr36 metallic glass at strain rates of 107/s, 108/s, and 109/s via classical molecular dynamics simulations to explore the underlying mechanism by which strain rate affects deformation behavior. It was found that strain rate has a great impact on the deformation behavior of metallic glass. The higher the strain rate is, the larger the yield strength. We also found that the strain rate changes the atomic structure evolution during deformation, but that the difference in the atomic structure evolution induced by different strain rates is not significant. However, the mechanical response under deformation conditions is found to be significantly different with the change in strain rate. The average von Mises strain of a system in the case of 107/s is much larger than that of 109/s. In contrast, more atoms tend to participate in deformation with increasing strain rate, indicating that the strain localization degree is more significant in cases of lower strain rates. Therefore, increasing the strain rate reduces the degree of deformation heterogeneity, leading to an increase in yield strength. Further analysis shows that the structural features of atomic clusters faded out during deformation as the strain rate increased, benefiting more homogeneous deformation behavior. Our findings provide more useful insights into the deformation mechanisms of metallic glass.

Comparative Study of Microstructure and Phase Composition of Amorphous-Nanocrystalline Fe-Based Composite Material Produced by Laser Powder Bed Fusion in Argon and Helium Atmosphere.

Laser powder bed fusion (LPBF) is a prospective and promising technique of additive manufacturing of which there is a growing interest for the development and production of Fe-based bulk metallic glasses and amorphous-nanocrystalline composites. Many factors affect the quality and properties of the resulting material, and these factors are being actively investigated by many researchers, however, the factor of the inert gas atmosphere used in the process remains virtually unexplored for Fe-based metallic glasses and composites at this time. Here, we present the results of producing amorphous-nanocrystalline composites from amorphous Fe-based powder via LPBF using argon and helium atmospheres. The analysis of the microstructures and phase compositions demonstrated that using helium as an inert gas in the LPBF resulted in a nearly three-fold increase in the amorphization degree of the material. Additionally, it had a beneficial impact on phase composition and structure in a heat-affected zone. The received results may help to develop approaches to control and improve the structural-phase state of amorphous-nanocrystalline compositional materials obtained via LPBF.

A tantalum-containing zirconium-based metallic glass with superior endosseous implant relevant properties.

Zirconium-based metallic glasses (Zr-MGs) are demonstrated to exhibit high mechanical strength, low elastic modulus and excellent biocompatibility, making them promising materials for endosseous implants. Meanwhile, tantalum (Ta) is also well known for its ideal corrosion resistance and biological effects. However, the metal has an elastic modulus as high as 186 GPa which is not comparable to the natural bone (10-30 GPa), and it also has a relative high cost. Here, to fully exploit the advantages of Ta as endosseous implants, a small amount of Ta (as low as 3 at. %) was successfully added into a Zr-MG to generate an advanced functional endosseous implant, Zr58Cu25Al14Ta3 MG, with superior comprehensive properties. Upon carefully dissecting the atomic structure and surface chemistry, the results show that amorphization of Ta enables the uniform distribution in material surface, leading to a significantly improved chemical stability and extensive material-cell contact regulation. Systematical analyses on the immunological, angiogenesis and osteogenesis capability of the material are carried out utilizing the next-generation sequencing, revealing that Zr58Cu25Al14Ta3 MG can regulate angiogenesis through VEGF signaling pathway and osteogenesis via BMP signaling pathway. Animal experiment further confirms a sound osseointegration of Zr58Cu25Al14Ta3 MG in achieving better bone-implant-contact and inducing faster peri-implant bone formation.

Laser-Based Additive Manufacturing and Characterization of an Open-Porous Ni-Based Metallic Glass Lattice Structure (Ni60Nb20Ta20).

Due to their amorphous structure, metallic glasses exhibit remarkable properties such as high strength, hardness, and elastic strain limit. Conversely, they also exhibit high susceptibility to brittle fracture, making them less qualified for the use as monolithic structural components. Therefore, they may be preferably used as the reinforcing phase in hybrid materials combined with ductile matrix materials. Especially metal matrix composites with interpenetrating structures are suitable. This requires an open-porous structure of the metallic glass. In the study at hand, an open-porous lattice structure was manufactured from metallic glass powder (Ni60Nb20Ta20) by laser powder bed fusion. A parameter study was carried out with various scanning strategies to manufacture a mechanically stable lattice structure while maintaining the amorphous structure of the metallic glass. Thus, X-ray diffraction measurements were conducted to validate the parameter study. A stable lattice structure with a largely amorphous structure was successfully achieved with a scanning strategy of single scanned lines and a rotation of 90° for each layer. However, nanocrystallization of 7% occurred in the heat-affected zones formed between the individual printed layers during reheating. Conducting compression tests, a compressive modulus of 18 GPa and a maximum strength of 90 MPa in 0°-direction were achieved. In 90°-direction, no compressive modulus could be determined but compressive strength resulted in 15 MPa. Performing nanoindentation with a Young's modulus of 195.1 GPa and Vickers hardness of HVIT = 956.1 was achieved for the printed bulk metallic glass alloy. The resulting lattice structure was further characterized by differential scanning calorimetry for thermal behavior.

Effect of Chemical Composition on the Thermoplastic Formability and Nanoindentation of Ti-Based Bulk Metallic Glasses.

A series of Ti41Zr25Be34-xNix (x = 4, 6, 8, 10 at.%) and Ti41Zr25Be34-xCux (x = 4, 6, 8 at.%) bulk metallic glasses were investigated to examine the influence of Ni and Cu content on the viscosity, thermoplastic formability, and nanoindentation of Ti-based bulk metallic glasses. The results demonstrate that Ti41Zr25Be30Ni4 and Ti41Zr25Be26Cu8 amorphous alloys have superior thermoplastic formability among the Ti41Zr25Be34-xNix and Ti41Zr25Be34-xCux amorphous alloys due to their low viscosity in the supercooled liquid region and wider supercooled liquid region. The hardness and modulus exhibit obvious variations with increasing Ni and Cu content in Ti-based bulk metallic glasses, which can be attributed to alterations in atomic density. Optimal amounts of Ni and Cu in Ti-based bulk metallic glasses enhance thermoplastic formability and mechanical properties. The influence of Ni and Cu content on the hardness of Ti-based bulk metallic glasses is discussed from the perspective of the mean atomic distance.

Intrinsic tensile ductility in strain hardening multiprincipal element metallic glass.

Traditional metallic glasses (MGs), based on one or two principal elements, are notoriously known for their lack of tensile ductility at room temperature. Here, we developed a multiprincipal element MG (MPEMG), which exhibits a gigapascal yield strength, significant strain hardening that almost doubles its yield strength, and 2% uniform tensile ductility at room temperature. These remarkable properties stem from the heterogeneous amorphous structure of our MPEMG, which is composed of atoms with significant size mismatch but similar atomic fractions. In sharp contrast to traditional MGs, shear banding in our glass triggers local elemental segregation and subsequent ordering, which transforms shear softening to hardening, hence resulting in shear-band self-halting and extensive plastic flows. Our findings reveal a promising pathway to design stronger, more ductile glasses that can be applied in a wide range of technological fields.

Universal origin of glassy relaxation as recognized by configuration pattern matching.

Relaxation processes are crucial for understanding the structural rearrangements of liquids and amorphous materials. However, the overarching principle that governs these processes across vastly different materials remains an open question. Substantial analysis has been carried out based on the motions of individual particles. Here, as an alternative, we propose viewing the global configuration as a single entity. We introduce a global order parameter, namely the inherent structure minimal displacement (IS Dmin), to quantify the variability of configurations by a pattern-matching technique. Through atomic simulations of seven model glass-forming liquids, we unify the influences of temperature, pressure and perturbation time on the relaxation dissipation, via a scaling law between the mechanical damping factor and IS Dmin. Fundamentally, this scaling reflects the curvature of the local potential energy landscape. Our findings uncover a universal origin of glassy relaxation and offer an alternative approach to studying disordered systems.

Kinetically Controlled Synthesis of Metallic Glass Nanoparticles with Expanded Composition Space.

Nanoscale metallic glasses offer opportunities for investigating fundamental properties of amorphous solids and technological applications in biomedicine, microengineering, and catalysis. However, their top-down fabrication is limited by bulk counterpart availability, and bottom-up synthesis remains underexplored due to strict formation conditions. Here, a kinetically controlled flash carbothermic reaction is developed, featuring ultrafast heating (>105 K s-1) and cooling rates (>104 K s-1), for synthesizing metallic glass nanoparticles within milliseconds. Nine compositional permutations of noble metals, base metals, and metalloid (M1─M2─P, M1 = Pt/Pd, M2 = Cu/Ni/Fe/Co/Sn) are synthesized with widely tunable particle sizes and substrates. Through combinatorial development, a substantially expanded composition space for nanoscale metallic glass is discovered compared to bulk counterpart, revealing that the nanosize effect enhances glass forming ability. Leveraging this, several nanoscale metallic glasses are synthesized with composition that have never, to the knowledge, been synthesized in bulk. The metallic glass nanoparticles exhibit high activity in heterogeneous catalysis, outperforming crystalline metal alloy nanoparticles.

Non-Isothermal Analysis of the Crystallization Kinetics of Amorphous Mg72Zn27Pt1 and Mg72Zn27Ag1 Alloys.

In this study, thin ribbons of amorphous Mg72Zn27Pt1 and Mg72Zn27Ag1 alloys with potential use in biomedicine were analyzed in terms of the crystallization mechanism. Non-isothermal annealing in differential scanning calorimetry (DSC) with five heating rates and X-ray diffraction (XRD) during heating were performed. Characteristic temperatures were determined, and the relative crystalline volume fraction was estimated. The activation energies were calculated using the Kissinger method and the Avrami exponent using the Jeziorny-Avrami model. The addition of platinum and silver shifts the onset of crystallization towards higher temperatures, but Pt has a greater impact. In each case, Eg > Ex > Ep (activation energy of the glass transition, the onset of crystallization, and the peak, respectively), which indicates a greater energy barrier during glass transition than crystallization. The highest activation energy was observed for Mg72Zn27Pt1 due to the difference in the size of the atoms of all alloy components. The crystallization in Mg72Zn27Ag1 occurs faster than in Mg72Zn27Pt1, and the alloy with Pt has higher (temporary) thermal stability. The Avrami exponent (n) values oscillate in the range of 1.7-2.6, which can be interpreted as one- and two-dimensional crystal growth with a constant/decreasing nucleation rate during the process. Moreover, the lower the heating rate, the higher the nucleation rate. The values of n for Mg72Zn27Pt1 indicate a greater number of nuclei and grains than for Mg72Zn27Ag1. The XRD tests indicate the presence of α-Mg and Mg12Zn13 for both Mg72Zn27Pt1 and Mg72Zn27Ag1, but the contribution of the Mg12Zn13 phase is greater for Mg72Zn27Ag1.