Amorphous Alloys Research Articles

Temperature effect on the passivation of a novel Fe-based metallic glass in simulated wet storage environment of spent nuclear fuels

Temperature effect on the passivation of a novel Fe-based metallic glass in simulated wet storage environment of spent nuclear fuels

Epsilon-near-zero thin films in a dual-functional system for thermal infrared camouflage and thermal management within the atmospheric window.

Thermal infrared camouflage aims to reduce the detectability of a target using thermal imaging devices. Given the typically high thermal emissivity in everyday environments, the thermal emissivity of the background environment must be considered. The conventional low-emissivity strategy for thermal camouflage is only effective for targets at extremely high temperatures (>350 °C), making it unsuitable for applications near room-to-medium-high temperature range (<350 °C). In this study, we introduce metallic glass into infrared thermal camouflage technology, exploiting its adjustable emissivity to accommodate diverse infrared thermal camouflage scenarios. Moreover, we combined metallic glass with the Berreman mode of epsilon-near-zero (ENZ) thin films (SiO2, Al2O3, and TiO2) for the first time. In the long wave infrared (LWIR, 8-14 μm) regions, the small viewing angle exhibits the optical properties of metallic glasses, while the large viewing angle (above 45°) provides high thermal emissivity in transverse-magnetic (TM) polarization. A thermal management function was provided without affecting the thermal camouflage performance. The cooling power exhibited by ENZ thin films on metallic glass surpassed that of the conventional low-emissivity strategy for thermal camouflage by a factor of 1.79. Furthermore, the thermal images indicated over 97% similarity in thermal radiation between the target and background environments. We developed a dual-function system for infrared camouflage and thermal management within an identical wavelength region of the atmospheric window.

Evaluating a Fe-Based Metallic Glass Powder as a Novel Negative Electrode Material for Applications in Ni-MH Batteries

Metallic glasses (MGs) are a type of multicomponent non-crystalline metallic alloys obtained by rapid cooling, which possess several physical, mechanical, and chemical advantages against their crystalline counterparts. In this work, an Fe-based MG is explored as a hydrogen storage material, especially, due to the evidence in previous studies about the capability of some amorphous metals to store hydrogen. The evaluation of an Fe-based MG as a novel negative electrode material for nickel/metal hydride (Ni-MH) batteries was carried out through cyclic voltammetry and galvanostatic charge–discharge tests. A conventional LaNi5 electrode was also evaluated for comparative purposes. The electrochemical results obtained by cyclic voltammetry showed the formation of three peaks, which are associated with the formation of Fe oxides/oxyhydroxides and hydroxides. Cycling charge/discharge tests revealed activation of the MG electrode. The highest discharge capacity value was 173.88 mAh/g, but a decay in its capacity was observed after 25 cycles, contrary to the LaNi5, which presents an increment of the discharge capacity for all the current density values evaluated, reached its value maximum at 183 mAh/g. Characterization analyses performed by X-ray diffraction, Scanning Electron Microscopy and Raman Spectroscopy revealed the presence of corrosion products and porosity on the surface of the Fe-based MG electrodes. Overall, the Fe-based MG composition is potentially able to work as a negative electrode material, but degradation and little information about storage mechanisms means that it requires further investigation.

Optimizing Manufacturing of Zr–Cu–AI–NI Metallic Glasses via Laser Metal Deposition

Recently, it was discovered that the cutting-edge technique known as laser powder bed fusion (LPBF) is the best way to produce Zr-based bulk glasses made of metal (BMGs). While LPBF gives greater versatility, current state-of-the-art production techniques like copper mold casting and arc-melting have limits when it comes to implementing complicated designs. Furthermore, LPBF enables a delicate balance to be struck between producing intricate characteristics and sustaining suitable temperatures all through the whole operation. Because of its exceptional features and practical availability, this research focuses on optimizing the process variables for a specific Zr-based alloy, AMZ4, which is produced by additive manufacturing in order to optimize both its mechanical and thermal characteristics. Belonging to the class of zirconium-based alloys known as bulk metallic glasses (BMG), Zr57Cu15Ni10AI5 (or Vit-106) has an excellent glass-forming ability and shows great promise. By casting, a BMG alloy may be transformed into workpieces that are about one centimeter in size in all three dimensions. Nevertheless, crystallization is induced when the cast size is further increased since it reduces the cooling rate. By building a workpiece from many melt sections with the cooling rate maintained above the critical one, selective laser melt (SLM) is an established technique for overcoming size restrictions for BMGs. Partially crystallized BMG is now an issue with SLM-obtained components. The effect of SLM process variables on partial crystallization is investigated in this paper. You may regulate the size and intensity of the inclusion by altering the speed of the laser scanning. Microhardness and wear resistance may be improved by incorporating submicron crystalline inclusions into the amorphous matrix by SLM.

Accelerated discovery of Magnesium-based amorphous alloys through a property-driven active learning strategy

Magnesium (Mg)-based amorphous alloys hold significant potential for applications in the automotive, aerospace, and biomedical industries. However, they are limited by their smaller size compared to other amorphous alloys. A higher reduced glass transition temperature (Trg) is associated with larger sizes in Mg-based amorphous alloys. Yet, due to the vast chemical space involved, designing Mg-based amorphous alloys with higher Trg using traditional ‘trial and error’ method is a challenging endeavor. In this work, we developed a property-driven active learning strategy to customize Mg-based amorphous alloys with enhanced Trg. After just two iterations, we successfully tailored four amorphous alloys with high Trg values. Under identical experimental conditions, two of these alloys exhibited Trg values surpassing that of Mg0·65Ag0·19Cu0.06Gd0.1, the alloy with best Trg value in the reported references. SHAP analysis revealed that Trg tends to be higher when the Ag atomic ratio exceeds 0.045, the Cu atomic ratio is below 0.18, the Ni atomic ratio is below 0.025, and the Mg atomic ratio is below 0.665. Our work offers a reliable strategy for designing Mg-based amorphous alloys with higher Trg and provides valuable insights for the rational design of these alloys.

The key to high-quality metallic glass casting: Interfacial reaction associated with vacuum induction melting process procedures

Even though vacuum induction melting (VIM) is widely employed in the industrial production of bulk metallic glasses (BMGs), the effect and mechanism of the interfacial reaction between the melt and the oxide ceramic crucible on BMG formations are not yet fully understood. Here, the influences and mechanisms of the interfacial reaction on a Zr-based BMG (Vit 105) subjected to various melting temperatures and holding times are revealed by employing experiments and theoretical calculations. We find that the degree of interfacial reaction is intriguingly correlated with the process parameters during VIM processing, leading to an increase in the oxygen content of the alloy and the reaction layer thickness. Besides, the increase of oxygen content also induces variations in the ordering and shear transformation zone (STZ) size of the BMGs, thus resulting in the precipitation of a nanoscale fcc phase and affecting the mechanical properties and reliability under deformation of the alloy. Furthermore, thermodynamic and kinetic parameters involved in the interfacial reaction, such as the molar Gibbs free energy of each element, the apparent activation energy, etc., are obtained, providing a comprehensive understanding of the transport processes at play. Our findings provide new insights into the preparation of BMGs by VIM and may be expanded to other melting techniques to accelerate the commercial application of metallic glasses.

Integrating dynamic relaxation with inelastic deformation in metallic glasses: Theoretical insights and experimental validation

Metallic glasses (MGs), a metastable material far from equilibrium, exhibit intricate dynamic relaxation behaviors. The challenge lies in developing a model that accurately describes the dynamics and deformation mechanisms of MG. This paper introduces a model integrating dynamic relaxation with deformation behavior. Validation through dynamic mechanical analysis, stress relaxation, creep, and strain recovery tests confirm the existence of four deformation modes: elasticity, anelasticity from β relaxation, anelasticity from α relaxation at low temperatures, and viscoplasticity from α relaxation at high temperatures. The model captures all of these deformation modes. The dynamical mechanical spectrum and stress relaxation spectrum unveil dynamic features during glass to liquid transition, and a simple and effective experimental method was developed for identifying ultra-low-frequency dynamic relaxation. This work provides new perspectives on the study of relaxation dynamics in glassy states and establishes important connections between dynamic relaxation behavior and deformation mechanisms. These findings lay a theoretical and experimental foundation for the broad application of MGs.

Design and characterization of biodegradable Mg−Zn−Ag metallic glasses

In order to develop the Mg−Zn−Ag metallic glasses (MGs) for biodegradable implant applications, the glass formation ability (GFA) and biocompatibility of Mg−Zn−Ag alloys were investigated using a combination of the calculation of phase diagrams (CALPHAD) and experimental measurements. High GFA potentiality of two alloy series, specifically Mg96−xZnxAg4 and Mg94−xZnxAg6 (x=17, 20, 23, 26, 29, 32, 35), was predicted theoretically and then substantiated through experimental testing. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were used to evaluate the crystallinity, GFA, and crystallization characteristics of these alloys. The results showed that compositions between Mg73Zn23Ag4 and Mg64Zn32Ag4 for Mg96−xZnxAg4, Mg66Zn28Ag6 and Mg63Zn31Ag6 for Mg94−xZnxAg6 displayed a superior GFA. Notably, the GFA of the Mg96−xZnxAg4 series was better than that of the Mg94−xZnxAg6 series. Furthermore, the Mg70Zn26Ag4, Mg74Zn20Ag6, and Mg71Zn23Ag6 alloys showed acceptable corrosion rates, good cytocompatibility, and positive effects on cell proliferation. These characteristics make them suitable for applications in medical settings, potentially materials as biodegradable implants.

Multi-layer formation by oxidation and solid-state crystallization of cold sprayed amorphous coatings during dry sliding wear

Amorphous alloy coatings, known for the exceptional wear resistance, have emerged as a key solution for enhancing the wear performance of magnesium alloys under harsh environments. In this study, Fe-based amorphous alloy coatings were deposited on magnesium alloy by cold spraying technology, and the influence of microstructural evolution on the wear performance of coatings under dry sliding wear conditions was discussed. The results showed that a dense adherent oxide layer with a thickness of ∼700 nm comprising nanograins of less than 8 nm was formed at the outmost surface, which played a role of self-lubricating. Underneath, a 1 μm thick nanocrystalline-amorphous layer with nanograins of ∼20 nm dispersed in the amorphous alloy matrix was formed through in-situ crystallization induced by flash temperature. This composite structure prevented the formation of shear bands in amorphous alloys and enhanced the durability. Therefore, the transition from abrasive wear to adhesive wear was a consequence of the microstructural evolution from a dual-phase composite layer to a self-lubricating oxide layer.

The temperature field characteristics and amorphous formation ability during the continuous casting process of Zr-based bulk metallic glass

This study utilized FLUENT dynamic mesh simulation technology to simulate the temperature field distribution characteristics during the continuous casting (CC) process of 5 mm thick Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 (Vit1) bulk metallic glass (BMG), analyzed and discussed the amorphous forming ability of the Vit1 BMG plate prepared through CC. The results indicate that during the CC process, the temperature gradient and cooling rate of Vit1 BMG plate decrease with increasing distance from the cooling copper block surface and prolonged solidification time. Even at the lowest cooling rate, it still remains significantly higher than the critical cooling rate (Rc) of Vit1 bulk amorphous alloy. The temperature variations recorded by the thermocouple during the alloy melt solidification process are in basic agreement with the simulation data. The experimental test and simulation results show that 5 mm thick Vit1 BMG slab can be prepared theoretically by continuous casting technology. Finally, XRD, DSC and TEM were used to analyze the amorphous formation ability and microstructure of the Vit1 BMG slab.

A strategy for designing Ti-based in-situ bulk metallic glass composites with tailored structural metastability using conventional titanium alloys

The metastability of the dendritic phase is crucial in determining the mechanical properties and mechanisms of the Ti-based in-situ dendrite-reinforced bulk metallic glass composites (BMGCs). However, tailoring the metastability effectively remains challenging. In this study, we propose a straightforward and effective strategy to tailor the dendrites composition and metastability using conventional Titanium alloys. Initially, six common Titanium alloys with increasing content of β-stabilizing elements such as Ti, Ti–6Al–4V, Ti–13Nb–13Zr, Ti–15Mo, Ti–12Mo–6Zr–2Fe and Ti-4.5Fe-6.8Mo-1.5Al were selected. Subsequently, a series of in-situ dendrite-reinforced BMGCs denoted as T1-T6 were designed by alloying these Titanium alloys with a specific amorphous alloy. It was found that the microstructure, stability and mechanical behaviors of these composites change significantly as the content of β-stabilizing elements in the dendritic phase increases monotonically. Based on their microstructure and mechanical behaviors, these composites can be classified into three categories: T1, T2 and T3, T4-T6. The T1 alloy exhibits brittle deformation characteristics due to the significantly higher elastic modulus of the dendritic phase. In contrast, the T2 and T3 alloys demonstrate good tensile plasticity and remarkable work-hardening ability, attributed to the metastable β phase undergoing stress-induced phase transformation during deformation. On the other hand, the T4-T6 alloys, consisting of stable β phase, deform via dislocation slip, resulting in a higher yielding stress and compression plasticity. The composition design strategy presented in this study, along with the correlation between mechanical behaviors and dendrite stability, may offer a novel perspective for the development of Ti-based in-situ dendrite-reinforced BMGCs.

Strengthening effects of indentation notches on metallic glasses and their sensitivity to stress triaxiality

In this study, a metallic glass sample with an annular indentation notch was successfully constructed by a compression rod cyclic compression strategy using molecular dynamics simulation, and the mechanical behaviors of cut-notched metallic glass samples with the same stress triaxiality and notch size under triaxial compression were comparatively analyzed. It is found that the indentation notch further improves the strength and plasticity of the metallic glass, while it is insensitive to the cut-notched metallic glass with the same notch size. During triaxial compression, rejuvenation and shear softening lead to an increase in free volume, while diffusion and residual compressive stresses lead to a decrease in free volume. The stress triaxiality plays a key regulatory role in their competition and affects the final state of free volume change. This study provides a new theoretical basis and process idea for the enhancement of strength and plasticity of metallic glass.

Crystallization path and non-isothermal kinetics of the Zr59.5Cu14.4Ni11.6Al9.7Nb4.8 metallic glass under different heating rates

In this work, the crystallization path and non-isothermal kinetics upon heating of the Zr59.5Cu14.4Ni11.6Al9.7Nb4.8 metallic glass were investigated. The devitrification process consists the formation of phases in the sequence of icosahedral quasicrystal (IQ) phase, Ni-containing phases, and Cu-containing phases. Avrami exponents were calculated at various heating rates, providing insights into the non-isothermal crystallization kinetics. The IQ phase and Ni-containing phases are interface-controlled growth, while the Cu-containing phases are diffusion-controlled growth. In addition, a continuous heating transition (CHT) diagram with a heating rate range exceeding six orders of magnitude was constructed, and the crystallization mechanism under different heating rates was revealed. These findings enrich the understanding of crystallization path and kinetics of metallic glass.

Molybdenum triggers the bifunctional mechanism of oxygen evolution reaction of Fe34-xNi25Co25MoxB8P8 amorphous alloy with boosted catalytic activity

High-valence metals (such as, Mo, W, Zr and Nb) have recently been reported that promote oxygen evolution reaction (OER) activity of the 3d-transition metal electrocatalysts. These high-valence metals play a key role on surface self-reconstruction process and stabilizing the low-valence active sites. However, further understand their effect on the OER mechanism is challenging, especially in amorphous electrocatalysts with complicated structure. Here, we integrate high-valence Mo with 3d metals (Fe, Co and Ni), fabricating Fe34-xCo25Ni25MoxP8B8 amorphous electrocatalysts by the melt-spinning method. We employ in-situ Raman spectroscopy to characterize the species evolution during OER, and find that the higher OER performance is originated from a bifunctional mechanism involves two catalytic sites (NiOOH and FeOOH) enabled by high-valence Mo dissolution. Benefit from this, the Fe34-xCo25Ni25MoxP8B8 with Mo show higher OER performance compared with Fe34-xCo25Ni25MoxP8B8 without Mo. For 3d-metal OER electrocatalyst, this study provides a new understanding on the effect of high-valence metals.

Formation, thermal stability and soft magnetic properties of Fe-Co-B-Si amorphous alloys with ultrahigh saturation magnetic induction of 2.0 T

This paper studies the influence of metallic element composition on the formation ability, thermal stability and magnetic properties of melt-spun (Fe1-xCox)B15–19Si1 (x =0.2–0.4) amorphous alloy ribbons. The maximum metal concentration at which an amorphous phase is formed during melt spinning has been determined in conjunction with the metal content dependence of crystallization processes and crystallized phases. The amorphous (Fe0.8Co0.2)84B15Si1 alloy with the highest metal content in an optimally annealed state exhibits an extremely high saturation induction (MS) of 2.0 T, low coercive force of 7.6 A m−1, high effective permeability of 13500 at 1 kHz and low core losses of 5.5 W kg−1 at 100 mT and 19.7 W kg−1 at 200 mT at 10 kHz which have not been simultaneously obtained for all kinds of soft magnetic materials up to date. The replacement of Fe with Co significantly increases the Curie temperature of the amorphous phase, resulting in very high thermal stability of the high MS alloys. The combination of excellent soft magnetic properties with ultrahigh MS value makes them candidates for use in highly loaded high-speed electric motors capable of operating at temperatures up to 473 K.

In-situ scattering and calorimetric studies of crystallization pathway and kinetics in a Cu-Zr-Al bulk metallic glass

The crystallization route and kinetics of a Cu-Zr-Al bulk metallic glass (BMG), based on Cu50Zr50, were investigated using in-situ synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS), in-situ high-energy X-ray diffraction (HEXRD), and differential scanning calorimetry (DSC). The acquisition of kinetic diagrams of SAXS/WAXS enables the direct construction of the overall phase transformation route from room temperature to the onset temperature of solid state phase transformation upon heating. It is revealed that the studied alloy undergoes multiple steps (at least five steps) before reaching the high-temperature thermodynamic equilibrium. This is distinct from the commonly believed simple path of glass → Cu10Zr7 + CuZr2 → B2-CuZr predicted by the Cu-Zr equilibrium phase diagram. In addition to thermodynamics, we emphasize that kinetic factors play a prominent role in the phase transformation process of Cu-Zr-Al BMGs. Furthermore, isothermal crystallization kinetics analyses conducted by in-situ HEXRD and DSC indicate that the formation of the initial crystalline phase, specifically the Cu10Zr7, follows an interface-controlled quasi-polymorphic process with an increasing nucleation rate. The findings of this study may provide novel insights into the crystallization mechanism of glass-forming supercooled liquids from a thermophysical perspective.

Achieve outstanding refrigeration performance near ambient temperature in a Fe88Pr8B2Ce2 amorphous ribbon

A novel Fe88Pr8B2Ce2 amorphous alloy (AA) with outstanding magnetocaloric effect near 295 K was vitrified into ribbon. The Fe88Pr8B2Ce2 ribbon exhibits a typical 2nd-order magnetic transition with a peak value of magnetic entropy change (−ΔSmpeak) of ∼ 4.34 J·kg−1·K−1 near its Curie temperature (Tc, ∼ 295 K) under 5 T, which is the highest among the AAs reported in the literature with Tc = 295±10 K. The temperature averaged entropy change (TEC) for the household air conditioner (TECAC) and refrigerator (TECR) were defined to evaluate the refrigeration performance of the magnetic refrigerants in these cooling facilities. TECAC and TECR for the Fe88Pr8B2Ce2 AA reach to 4.21 J·kg−1·K−1 and 3.93 J·kg−1·K−1, both of which are also much larger than those of other AAs with Tc near 295 K and indicate the better application perspective of the Fe88Pr8B2Ce2 AA as the magnetic refrigerants working in the residential magnetic air conditionings and refrigerators.

Experimental investigation of comprehensive performance by tailoring the proportion of late transition metals in quinary Fe-Co-Ni-Si-B amorphous alloys

We fabricated the Fe-Co-Ni-Si-B multi-principal element alloys by vacuum melt-spinning method. The effects of late transition metals proportion in quinary alloy ribbons on the formation, phase structure, thermal stability, microhardness, corrosion resistance and soft magnetic properties were investigated. The melt-spun structure consists of an amorphous single phase for all the specimens. The surfaces of glassy ribbons are rather flat and flawless and the average surface roughness is 0.351 nm or below. The initial crystallization temperature (Tx) and supercooled liquid region (ΔTx) of alloy system decrease by degrees with increasing Co and Ni content, showing the maximum values of 753.0 K and 60.0 K for Fe60Co10Ni10Si6B14 alloy. But the glass transition temperature (Tg) seems to barely change and maintain approximately 692.0 K. All the as-received alloy ribbons exhibit good bending ductility and acceptable Vickers microhardness ranging from 671 to 785 HV0.5. The amorphous alloy ribbons present a gradually wide passive potential range (ΔE) with the decrease of Fe content, but the corrosion current density (Icorr) becomes larger. The smallest Icorr value is 1.785 μA·cm-2 for Fe60Co10Ni10Si6B14 alloy and the widest ΔE value is about 0.272 V for Fe26Co27Ni27Si6B14 alloy. The saturation magnetization of these glassy alloys reduces from 165.0 to 112.0 emu/g as the Fe content decreases. Meanwhile, the coercivity also changes from 14.25 to 6.70 A/m. This paper offers a brand-new perspective to understand the role of late transition metals on the various physicochemical properties of quinary Fe-Co-Ni-Si-B amorphous alloys.

FeSiBCCr bulk metallic glasses with excellent soft magnetic properties prepared using spark plasma sintering technology

Fe-based amorphous alloys have received much attention in the fields of electronics and electrical due to their excellent soft magnetic properties at high frequency. However, the controllable preparation of large-sized Fe-based bulk metallic glasses (BMGs) still faces numerous challenges. In this study, FeSiBCCr amorphous powders prepared by gas-water combined atomization were used as raw materials, and FeSiBCCr BMGs were prepared through spark plasma sintering (SPS) at different pressures. The microstructure, phase and magnetic properties of the compacts were systematically characterized using SEM, XRD, TEM, DSC, and VSM. The results showed that when the sintering pressure was 50 MPa, the slow densification process dominated by particle rearrangement at the initial densification process made the internal contact resistance of the compacts larger. This led to macroscopic inhomogeneous physical fields and severe local overheating during the later stages of sintering, causing the precipitation of α-(Fe, Si) and Fe3B phases. Although the material exhibited a relatively high saturation magnetization (Bs) of 1.08 ± 0.01 T, the low density and amorphous fraction resulted in a high coercivity (Hc) of 1060.8 ± 37.8 A·m-1. When the sintering pressure was increased to 250 MPa, the degree of particle densification significantly improved, and the temperature inhomogeneity was markedly suppressed due to reduced internal resistance. Thus, the prepared FeSiBCCr BMGs exhibited an extremely high density of 6.66 ± 0.06 g·cm-3 and excellent soft magnetic properties with Bs of 1.23 ± 0.01 T and Hc of 18.8 ± 1.8 A·m-1. This indicated that the FeSiBCCr BMGs prepared in this study exhibited broad application prospects in efficient electromagnetic conversion and advanced electronic devices.

Structural Relaxation and Delayed Yielding in Cyclically Sheared Cu-Zr Metallic Glasses

Structural Relaxation and Delayed Yielding in Cyclically Sheared Cu-Zr Metallic Glasses