Amorphous Alloys Research Articles

Prediction of the thermal-physical properties of amorphous nickel alloys Ni2B, Ni44Nb56, Ni62Nb38 according to component data

The replacement of traditional materials with amorphous alloys and the operation of products made from them are determined by the structural, temporal and temperature stability of disordered environments. In particular, the thermal stability of an amorphous alloy directly depends on its thermophysical characteristics. Therefore, the article demonstrates the applicability of the rule of mixing components and the use of their data on thermophysical properties in the crystalline state to evaluate similar characteristics of alloys from the metal – metalloid and transition metal – transition metal groups in the amorphous phase. It has been established that for the transition metal – transition metal group, the assessment of the heat capacity of amorphous nickel alloys gives a better approximation to the experimentally established values than for an alloy from the metal – metalloid group. The reasons for the discrepancy between the assessment and experimental data for an alloy from the metal – metalloid group are possibly the covalency of the atomic bonds in contrast to the metallic bond for alloys from the transition metal – transition metal group, the smaller size of the metalloid atoms, its greater mobility and the effect on the refinement of alloy grains. The possibility of an amorphous alloy inheriting some properties of one of the components is indicated, which requires experimental verification.

Study on the mechanism of crystal-induced plasticity enhancement in Ni-Zr crystal/amorphous composites by molecular dynamics simulation

The industrial applications of metallic glass (MGs) are limited by poor plasticity, which crystal/amorphous composites (CACs) can effectively address. This study simulates the compression of Ni-Zr MGs with embedded fcc crystal phases by molecular dynamics to elucidate the mechanism of crystal-induced plasticity enhancement. The plasticity of CACs improves with larger crystal sizes. Atoms at the crystal-amorphous interfaces (CAIs) are classified as CAIfcc and CAIMGs for fcc and MGs, respectively. The transformation of CAIfcc to CAIMGs at the CAIs is crucial for plastic flow during compression. The connection between CAIfcc and CAIMGs clusters is less stable than that of fcc, making it more prone to damage and leading to multiple shear bands (SBs). These SBs offer additional pathways for plastic flow, reducing stress concentration and enhancing material plasticity. This research provides an atomic-level understanding of crystal-induced plasticity in CACs, offering valuable insights for designing high-performance CACs.

Excellent Magnetocaloric Properties near 285 K of Amorphous Fe88Pr6Ce4B2 Ribbon

A novel amorphous Fe88Pr6Ce4B2 ribbon with better magnetocaloric properties near 285 K is reported in the present work. The Fe88Pr6Ce4B2 ribbon exhibits a typical second-order ferromagnetic–paramagnetic transition near its Curie temperature (Tc, ~284 K), with a maximum magnetic entropy change (−ΔSmpeak) of ~4.15 J/(kg × K) under 5 T and a maximum adiabatic temperature rise (ΔTad) of ~2.57 K under 5 T, both of which are almost the largest amongst the iron-based metallic glasses with Tc = 285 ± 10 K. The high −ΔSmpeak enables several amorphous hybrids with table-like −ΔSm–T curves to be synthesized by appropriately proportioning the Fe88Pr6Ce4B2 ribbon and other amorphous ribbons with different Tc. The larger average −ΔSm and effective refrigeration capacity, as well as the appropriate temperature range, make the two amorphous hybrids potential candidates for use as refrigerants in household magnetic air conditioners.

Electrochemical production of ammonia: Nitrate reduction over novel Cu-Ni-Al metallic glass nanoparticles used as highly active and durable catalyst

It is a great challenge to design and synthesize catalysts that can regulate both adsorption and desorption processes for electrocatalytic nitrate reduction to ammonia (NRA). Herein, amorphous Cu-Ni-Al nanometallic glasses (NG) were synthesized using a facile thermal evaporation coupled Joule heating method. The Cu50Ni25Al25-NG exhibits remarkable Faradaic efficiency (98.81 %) and NH3 yield-rate (211.14 μmol h−1cm−2) at an outstanding positive potential of −0.15 V vs. RHE. Aluminum atoms of low work-function when intercalated at different positions in Cu50Ni25Al25-NG enhance both adsorption and desorption processes during NRA. The oscillatory properties of surface potential detected by Kelvin-probe force microscopy demonstrate the diversity of active sites on Cu50Ni25Al25-NG. Two potential-regulated reaction mechanisms in NRA on the surface of Cu50Ni25Al25-NG were proposed using in-situ electrochemical Raman spectra. This work provides a new method for the preparation of multi-element NG enriched with low work-function metals and a new idea for the synthesis of synergistic catalytic-sites for NRAs.

Non-Equal Contributions of Different Elements and Atomic Bonds to the Strength and Deformability of a Multicomponent Metallic Glass Zr47Cu46Al7.

Multicomponent metallic glasses (MGs) are a fascinating class of advanced alloys known for their exceptional properties such as limit-approaching strength, high hardness and corrosion resistance, and near-net-shape castability. One important question regarding these materials that remains unanswered is how the different elements and atomic bonds within them control their strength and deformability. Here, we present a detailed visual and statistical analysis of the behaviors of various elements and atomic bonds in the Zr47Cu46Al7 (at%) MG during a uniaxial tensile test (in the z-direction) simulated using molecular dynamics. Specifically, we investigate the identities of atoms undergoing significant shear strain, and the averaged bond lengths, projected z-lengths, and z-angles (angles with respect to the z-direction) of all the atomic bonds as functions of increasing strain. We show that, prior to yielding, the Zr element and the intermediate (Zr-Zr, Cu-Al) and stronger (Zr-Al, Zr-Cu) bonds dominate the elastic deformation and strength, while the Cu and Al elements and the weaker Al-Al and Cu-Cu bonds contribute more to the highly localized shear transformation. The significant reconstruction, as signified by the cessation of bond-length increment and bond-angle decrement, of the intermediate and the stronger bonds triggers yielding of the material. After yielding, all the elements and bonds participate in the plastic deformation while the stronger bonds contribute more to the residual strength and the ultimate (fracture) strain. The results provide new insights into the atomic mechanisms underlying the mechanical behavior of multicomponent MGs, and may assist in the future design of MG compositions towards better combination of strength and deformability.

Improving the photoswitching performance of a transistor with amorphous metal oxide semiconductor thin film by a gradient annealing approach

Metal oxides are attracting attention as electronic mate rials in research and industry. Thin films of amorphous indium gallium zinc oxide (a-IGZO) exhibit low absorbance in the visible spectrum, making them ideal components in transparent electronics. To widen the scope of use for thin film transistor (TFT) devices based on a-IGZO in on-chip sensing applications, photoresponsive behavior has been achieved by proper engineering of the active layers by either introducing a photosensitive top layer or using a method to generate localized states inside the band gap. In this paper, we propose a bilayer structured with the use of thermal annealing of a-IGZO film at different temperatures. Thermal annealing has been shown to improve the electrical performance of the TFT devices because of the improved film quality but negatively affects the photoresponsivity by removing tarp sites that play an important role in both charge generation and photomultiplication via the photogating effect. Therefore, here we propose an a-IGZO film with a high temperature-annealed bottom layer and pristine top layer. The bottom layer plays a vital role in the charge transport behavior, resulting in a low threshold voltage and subthreshold swing similar to the device with a fully annealed film, while the photoresponse of the device is driven by the higher density of gap states in the pristine top layer. This proposed method is advantageous to previously published procedures due to the simplicity of using no additional materials and complex steps to introduce trap sites into the photoactive layer, but only differential annealing temperature.

Fabrication and comprehensive evaluation of Zr-based bulk metallic glass matrix composites for biomedical applications

AbstractThe aim of this study is to fabricate Zr-based bulk metallic glass matrix composites (BMG-MCs) for biomedical usage and subject them to a comprehensive and farreaching analysis with respect to their mechanical properties, biocorrosion resistance, biocompatibility, and interactions with biofilms that all may arise from their chemical compositions and unusual disordered internal structure. In this study, we fabricate Zr40Ti15Cu10Ni10Be25, Zr50Ti15Cu10Ni10Be25, and Zr40Ti15Cu10Ni5Si5Be25 alloys and confirm their glassy matrix nature through differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) analyses. The mechanical properties, assessed via nanoindentation, demonstrate the high hardness, strength, and elasticity of the produced materials. Corrosion resistance is investigated in simulated body fluid, with Zr-based BMG-MCs exhibiting superior performance compared to conventional biomedical materials, including 316L stainless steel and Ti6Al4V alloy. Biocompatibility is assessed using human fetal osteoblastic cell line hFOB 1.19, revealing low levels of cytotoxicity. The study also examines the potential for biofilm formation, a critical factor in the success of biomedical implantation, where bacterial infection is a major concern. Our findings suggest, as never reported before, that Zr-based BMG-MCs, with their unique composite glassy structure and excellent physicochemical properties, are promising candidates for various biomedical applications, potentially offering improved performance over traditional metallic biomaterials.

A novel grain refinement of Ce-Fe-B magnets induced by magnetic field annealing

Magnetic field annealing-induced grain refinement usually occurs during the crystallization process of amorphous alloys. This work investigates the effects of magnetic field annealing on the microstructure and magnetic properties of crystalline Ce17Fe76Co1Zr0.5B6Mo0.5 alloys. The results indicate that magnetic field annealing below the Curie temperature (TC) of the Ce2Fe14B phase in the alloys reduces the alloy’s grain size. At an annealing temperature of 433 K, the average grain size of alloys decreased from 48.0 nm in the as-spun sample to 27.2 nm in the magnetic field annealing sample. Moreover, magnetic field annealing can effectively reduce the volume fraction of the CeFe2 phase in the alloy. After magnetic field annealing at 433 K, the alloy obtained the optimal comprehensive magnetic properties: the intrinsic coercivity (Hci = 441.1 kA/m), remanence (Br = 0.49 T), squareness (Hk/Hci = 0.53), and maximum energy product ((BH)max) = 35.5 kJ/m3), which were 0.2 %, 16.7 %, 6 %, and 29.1 % higher than the values of the as-spun sample, respectively. Precession electron diffraction (PED) analysis revealed that magnetic field annealing increased strain at grain and phase boundaries and a more uniform grain orientation spread (GOS), promoting recrystallization and grain refinement. This study provides new insights into the grain refinement mechanism of crystalline alloys under magnetic field annealing, contributing to further improving the magnetic properties of Ce-Fe-B magnets.

Corrosion behavior of Zr55Cu30Al10Ni5 amorphous alloy produced by two-roll strip casting in aqueous environments

Corrosion behavior of Zr55Cu30Al10Ni5 amorphous alloy produced by two-roll strip casting in aqueous environments

Restructuring the interfacial active sites to generalize the volcano curves for platinum-cobalt synergistic catalysis

Computationally derived volcano curve has become the gold standard in catalysis, whose practical application usually relies on empirical interpretations of composition or size effects by the identical active site assumption. Here, we present a proof-of-concept study on disclosing both the support- and adsorbate-induced restructuring of Pt-Co bimetallic catalysts, and the related interplays among different interfacial sites to propose the synergy-dependent volcano curves. Multiple characterizations, isotopic kinetic investigations, and multiscale simulations unravel that the progressive incorporation of Co into Pt catalysts, driven by strong Pt-C bonding (metal-support interfaces) and Co-O bonding (metal-adsorbate interfaces), initiates the formation of Pt-rich alloys accompanied by isolated Co species, then Co segregation to epitaxial CoOx overlayers and adjacent Co3O4 clusters, and ultimately structural collapse into amorphous alloys. Accordingly, three distinct synergies, involving lattice oxygen redox from Pt-Co alloy/Co3O4 clusters, dual-active sites engineering via Pt-rich alloy/CoOx overlayer, and electron coupling within exposed alloy, are identified and quantified for CO oxidation (gas-phase), ammonia borane hydrolysis (liquid-phase), and hydrogen evolution reaction (electrocatalysis), respectively. The resultant synergy-dependent volcano curves represent an advancement over traditional composition-/size-dependent ones, serving as a bridge between theoretical models and experimental observations in bimetallic catalysis.

The role of C content on the glass-forming ability and magnetic properties of FeSiBPC amorphous alloys

The role of C content on the glass-forming ability and magnetic properties of FeSiBPC amorphous alloys

Analysis of shear bands in bulk metallic glasses based on elastoplastic phase transformation theory

Abstract Shear bands in amorphous alloys have been widely observed in uniaxial tension and compression experiments, reflecting strain localization, with plastic deformation occurring within the shear bands. In many instances, failures of bulk metallic glasses (BMGs) occur along the dominant shear bands. In this study, phase transformation theory is applied to investigate the mechanical properties of shear bands, focusing on the analysis of the two-phase deformations. The shear bands and the regions outside them are treated as two distinct phases in equilibrium. The deformation gradient tensor across the interface between these phases is discontinuous. By applying the jump conditions, governing equations are derived. As a case study, the shear bands and surrounding regions of plastic BMGs under uniaxial compression are analyzed, enabling the calculation of the stress associated with phase transformation and the inclination angle of the shear bands. The results obtained from this theoretical model align well with existing experimental and simulation data.

Magnetoimpedance Effect in Cobalt-Based Amorphous Alloy Irradiated by Nickel and Hydrogen Ions

Magnetoimpedance Effect in Cobalt-Based Amorphous Alloy Irradiated by Nickel and Hydrogen Ions

Optimizing Ni-Zr-Ti metallic glasses: Cluster design and molecular dynamics evaluation of glass forming ability

Ni-based metallic glasses have garnered significant attention due to their excellent mechanical properties and wide application prospects. However, their low glass forming ability (GFA) limits broader applications. This study explores the Ni-Zr-Ti ternary system, which excludes precious metals, using clusters and mixing entropy composition design method to develop a series of Ni-based metallic glasses with improved GFA. The study found that the composition Ni60.91Zr24.97Ti14.12 (NZT3) had the best GFA, with its cluster expression Ni-Ni8Ti4 + 1.17838 Ni-Ni6Zr6. To gain a deeper understanding of the GFA of metallic glasses, molecular dynamics (MD) simulations were conducted on the designed compositions. The simulation results indicated a significant correlation between the average local five-fold symmetry (ALFFS) and the GFA of the compositions. Ni60.91Zr24.97Ti14.12 exhibited the highest ALFFS value and the best GFA. The research demonstrates that by combining clusters and mixing entropy composition design method with the simulated ALFFS, metallic glasses with excellent GFA in the Ni-Zr-Ti system can be rapidly screened. The successful application of this innovative approach in this system not only deepens the understanding of metallic glass formation mechanisms but also provides significant guidance for future materials design.

Unveiling the boson peaks in amorphous phase-change materials

The Boson peak is a universal phenomenon in amorphous solids. It can be observed as an anomalous contribution to the low-temperature heat capacity over the Debye model. Amorphous phase-change materials (PCMs) such as Ge-Sb-Te are a family of poor glass formers with fast crystallization kinetics, being of interest for phase-change memory applications. So far, whether Boson peaks exist in PCMs is unknown and, if they do, their relevance to PCM properties is unclear. Here, we investigate the thermodynamic properties of the pseudo-binary compositions on the tie-line between Ge15Te85and Ge15Sb85from a few Kelvins to the liquidus temperatures. Our results demonstrate the evidence of the pronounced Boson peaks in heat capacity below 10 K in the amorphous phase of all compositions. By fitting the data using the Debye model combined with a modification of the Einstein model, we can extract the characteristic parameters of the Boson peaks and attribute their origin to the excess vibrational modes of dynamic defects in the amorphous solids. We find that these parameters correlate almost linearly with the Sb-content of the alloys, despite the nonmonotonic behaviors in glass forming abilities and thermal stabilities. In a broader context, we show that the correlations of the characteristic parameters of the Boson peaks with Tg and kinetic fragility, vary according to the type of bonding. Specifically, metallic glasses and conventional covalent glasses exhibit distinct patterns of dependence, whereas PCMs manifest characteristics that lie in between. A deeper understanding of the Boson peaks in PCMs holds the promise to enable predictions of material properties at higher temperatures based on features observed in low-temperature heat capacity.

Understanding the stretched exponential decay of strained metallic glasses by a free-volume model

Understanding the stretched exponential decay of strained metallic glasses by a free-volume model

Modulating the rejuvenation in a Al75Mg25 metallic glass by multiple recovery annealing treatment

Rejuvenation presents a promising way to improve the plasticity of metallic glasses. How modulating the degree of rejuvenation of metallic glasses remains a challenging issue. Here, based on the molecular dynamics simulation, we investigate the evolution of the structural and mechanical properties of a binary Al75Mg25 metallic glass and successfully realized the rejuvenation modulation through the multiple recovery annealing treatment. A range of samples with different degrees of rejuvenation were obtained by successive multiple recovery annealing process. According to our calculations, we found that the degree of rejuvenation is highly correlated with the Al-centered clusters. Microstructural analyses show that a higher degree of rejuvenation is concomitant with less 1551 index of Honeycutt-Andersen indices and a lower content of <0,0,12,0 > in terms of Voronoi Tessellation analysis. Moreover, our calculated results demonstrate that the samples with the aging initial state show a higher degree of rejuvenation as compared to the samples with the rejuvenated initial state. This can be attributed to that there are more icosahedral clusters, which are more likely to change to other types of clusters with low local fivefold symmetry in the aged samples during the subsequent high-temperature annealing process. Our work confirms that proper multiple (no more than three times) recovery annealing treatment can increase the degree of rejuvenation of metallic glasses and can offer a better understanding of the effect of rejuvenation on the microstructures and mechanical properties of metallic glasses.

Dependence of structures and performances of soft-magnetic FeCo-based metal glasses on cryogenic treatments

The amorphous structures, thermal stability, soft-magnetic properties and microhardness have been explored for quaternary quenched (Fe0.8Co0.2)75B21Ta4 (Fe0.8) and (Fe0.5Co0.5)75B21Ta4 (Fe0.5) metallic glasses (MGs) after deep (77 K), moderate (173 K) and shallow (253 K) cryogenic treatments (CTs). Compared to Fe0.5, the as-spun Fe0.8 exhibits significantly higher thermal stability and Curie temperature (686 K), which could be explained by the Mössbauer spectra results of higher A23 and lower hyperfine magnetic field as well as isomer shift. But the as-spun Fe0.5 shows a more prominent magnetic rejuvenation trend. Additionally, the observation of magneto-optic Kerr microscope displays that magnetic domains around surface defects exhibit a trend from being easy to magnetize to becoming difficult with increasing reverse magnetic field intensity.The cryo-treated Fe0.8 and Fe0.5 ribbons maintaining a completely amorphous structure reveal the improved soft-magnetic property and microhardness, and the performance optimization of Fe0.5 is more sensitive to CTs. Appropriate CTs distinctly decrease coercivity (Hc) of two tested MGs, and moderate CT reduces the Hc of Fe0.5 by 24.1%, achieving commendable magnetic softening. The Hc variation can be rationalized by the evolution of free volume in the amorphous matrix involving freezing, partial annihilation and imbalance under different CTs. Moreover, shallow CT significantly expands the heat-treatment processing window of MGs.

Synthesis of High-Thermally Stable Ni60Nb13.3Zr13.3Ti13.3 Amorphous Alloy by Mechanical Alloying

Synthesis of High-Thermally Stable Ni60Nb13.3Zr13.3Ti13.3 Amorphous Alloy by Mechanical Alloying

A novel strategy to significantly improve wear resistance of amorphous alloys by immersion in NaOH solution

The application of amorphous alloys in tribology is constrained by their inherent brittleness. An alkaline treatment (AT) can address this limitation by hydrogen generated rejuvenation. Following AT in a 3 mol/L NaOH solution for 3 days, the hardness of as-cast Ti-based amorphous alloys decreased by about 10 %, while the relaxation enthalpy increased approximately 2.2 times. Concurrently, the average coefficient of friction (COF) decreased by more than 15 % under all test loads except at 10 N. Additionally, the wear rate significantly decreased by over 20 %, with a notable reduction of about 25 % under a 7 N load. The improvements in tribological properties are primarily attributed to increased plasticity and surface oxidative ability, resulting from the hydrogen absorption during chemical reactions. Thus, AT offers a practical and effective way to significantly enhance the tribological performance of amorphous alloys.