Structure Of Amorphous Alloys Research Articles

Effects of the Substitution of B and C for P on Magnetic Properties of FePCB Amorphous Alloys

In the present study, first-principles molecular dynamics simulations were employed to study the effects of small amounts of B and C substituted for P on the structure and magnetic properties of Fe80P13C7, Fe80P10C7B3, and Fe80P8C9B3 amorphous alloys. A small amount of B and C replacing P atoms increases the icosahedral structure of the amorphous alloys, especially the increase in the regular icosahedral structure. The saturation magnetization of the three kinds of amorphous alloys gradually increases with the addition of B and C atoms, and the results of experimental and simulated calculations show consistent trends. The substitution of P atoms by B and C atoms leads to the aggregation of Fe atoms, which increases the magnetic moment of the iron atoms. In addition, the improvement of local structural symmetry may be one of the reasons for the increase in saturation magnetization of amorphous alloys. The substitution of a small number of B and C atoms plays an important role in improving the saturation magnetization of the amorphous alloy, which has a certain guiding significance for the development of amorphous alloys with excellent soft magnetic properties.

Effect of Y element on atomic structure, glass forming ability, and magnetic properties of FeBC alloy

Abstract The atomic structure of amorphous alloys plays a crucial role in determining both their glass-forming ability and magnetic properties. In this study, we investigate the influence of adding the Y element on the glass-forming ability and magnetic properties of Fe86−x Y x B7C7 (x = 0, 5, 10 at.%) amorphous alloys via both experiments and ab initio molecular dynamics simulations. Furthermore, we explore the correlation between local atomic structures and properties. Our results demonstrate that an increased Y content in the alloys leads to a higher proportion of icosahedral clusters, which can potentially enhance both glass-forming ability and thermal stability. These findings have been experimentally validated. The analysis of the electron energy density and magnetic moment of the alloy reveals that the addition of Y leads to hybridization between Y-4d and Fe-3d orbitals, resulting in a reduction in ferromagnetic coupling between Fe atoms. This subsequently reduces the magnetic moment of Fe atoms as well as the total magnetic moment of the system, which is consistent with experimental results. The results could help understand the relationship between atomic structure and magnetic property, and providing valuable insights for enhancing the performance of metallic glasses in industrial applications.

EXPLORING AMORPHOUS ALLOYS: ADVANCED ELECTRON MICROSCOPY AND CLUSTER ANALYSIS

In this study, we explored the atomic structure and orderliness of amorphous alloys through advanced electron microscopy and analytical techniques. Amorphous alloys, characterized by disordered atomic structures, exhibit promising applications in technology. The research addresses a crucial knowledge gap by investigating cluster distribution, particle arrangement, and orderliness within the amorphous matrix. High-resolution electron microscopy (HREM) images are analyzed using diverse algorithms and software tools. The study establishes a correlation between angles approaching 180 degrees and increased orderliness within clusters, highlighting the reliability of angle distribution analysis. Robust indicators, including Div (SP(B/V)) and Div (Mu(B/V)) metrics, assess and compare amorphous alloy samples. Kullback-Leibler (K-L) divergence indicates the significance of cluster ordering, validated by the S-K test. Radial Distribution Function (RDF) analysis uncovers local short-range order, deepening understanding despite limited orderliness discernment. These findings not only enhance our understanding of metallic glasses or amorphous alloys but also offer opportunities for tailored design and improved applications across various technological domains.

ADVANCED ELECTRON MICROSCOPY IMAGE PROCESSING FOR ANALYZING AMORPHOUS ALLOYS: ELECTRON MICROSCOPY IMAGE CLUSTER ANALYZER (EMICA). TOOL AND RESULTS

This article unveils EMICA, a Python-based software tool revolutionizing electron microscopy image processing for amorphous alloys. EMICA addresses the unique challenges posed by these materials, which lack long-range order, by providing specialized capabilities for cluster analysis and spatial pattern recognition. This research explored software tool development and application through illustrative examples, answering the key question of how they enhance amorphous alloy analysis. By integrating advanced image processing techniques and algorithms, EMICA uncovers hidden patterns, offering quantitative insights into cluster distributions. The key message emphasizes the application's transformative impact on material science research, providing a specialized solution for electron microscopy image analysis in the amorphous alloy domain. Our key findings, presented through real-world examples and case studies, attest to the efficacy of the software in revealing nuanced details of amorphous alloy structures. From identifying subtle variations in atomic configurations to quantifying cluster distributions, EMICA represents a significant leap forward in the field of advanced electron microscopy image processing, contributing significantly to the advancement of this domain.

Shear bands in amorphous alloys and their role in the formation of nanocrystals

The processes of evolution of the structure and surface morphology of Al87Ni8La5 and Fe76Si13B11 amorphous alloys under deformation have been studied. It is shown that the deformation occurs through the formation and propagation of shear bands, which form steps when they reach the surface. The formation of nanocrystals in shear bands was noted. It is shown that steps on the surface are formed under the combined action of several elementary shear bands. Shear bands have a variable thickness in the range from 5 to 20 nm. An elementary step has a thickness of about 15 nm. Shear bands can be combined into zones. The transverse size of the zones is about 1 μm. The formation of nanocrystals in zones can lead to anisotropy in the orientational position of nanocrystals in an amorphous matrix. With an increase in the degree of deformation, nanocrystals are formed not only in shear bands, but also in areas adjacent to them. There is a difference in the kinetics of the formation of nanocrystals in an alloy based on aluminum and iron.

Probing microstructural heterogeneity of La-based amorphous alloy under versatile mechanical stimuli

The intrinsic structural heterogeneity of amorphous alloy is closely related to the thermodynamics and dynamical behavior, such as relaxation/crystallization, glass transition and plastic deformation. However, the structural information is submerged into the meta-stable disordered long-range structure, which makes it very difficult to explore the structural heterogeneity of amorphous alloy. A mechanical excitation factor is insufficient to effectively describe the heterogeneity of the microstructure in amorphous alloy, particularly the correlation between structure and dynamics. To explore the essence of the structure in amorphous alloy, it is necessary to consider the different mechanical stimuli. La<sub>62</sub>Cu<sub>12</sub>Ni<sub>12</sub>Al<sub>14</sub> amorphous alloy is selected as the model system, dynamic mechanical process is probed by dynamic mechanical analyzer (DMA). The contributions of <i>α</i> relaxation process and <i>β</i> relaxation process are described in the framework of the quasi-point defect theory. Based on the quasi-point defect theory, the <i>α</i>-relaxation and <i>β</i>-relaxation in the La-based amorphous alloy are separated. Tensile strain rate jump measurements are conducted to study the high temperature rheological behavior of amorphous alloy. The contributions of elasticity, anelasticity, and plastic deformation during the homogeneous flow of amorphous alloy are determined within the framework of quasi-point defect theory. The present work aims to reveal the structural heterogeneities of amorphous alloys under the action of dynamics on various temporal scales. The physical background of the activation, propagation and coalescence of defects in amorphous alloy under different mechanical stimuli are reviewed.

Optimizing stress impedance and medium-range ordered structure in Fe46.6Mo8.6Cr24.5B9.5C10Si6 amorphous alloy through tailored annealing treatment

Amorphous alloys are emerging as a highly promising category of materials for mechanical sensing, attributed to their favorable stress impedance performance. However, the practical achievement of the stress impedance ratio still falls considerably short of its theoretical potential, and the atomic-scale mechanisms underlying this phenomenon remain largely unexplored. Here, we report that the stress impedance ratio of Fe46.6Mo8.6Cr24.5B9.5C10Si6 amorphous alloy can be significantly enhanced by a tailored annealing treatment around the glass transition temperature (Tg), giving rise to the highest stress impedance ratio reaching up to 124%. Utilizing the high-energy synchrotron X-ray total scattering technique, the strong correlation between the stress impedance performance and the medium-range ordered structure of amorphous alloys is elucidated. Our findings revealed that an increase in edge-sharing atomic connection mode plays a pivotal role in enhancing the stress impedance performance. Furthermore, a composite film combining the amorphous alloy with silicone rubber was fabricated under the same annealing treatment, demonstrating a significantly improved sensitivity compared to the ribbon (706.10 MPa-1 vs. 32.93 MPa-1). This work not only contributes valuable insights into the atomic-scale mechanisms governing stress impedance in amorphous alloys but also proposes a general annealing strategy that holds the potential for unlocking new avenues in advanced sensing applications.

Relationship between relaxation embrittlement and atomic cluster structure in amorphous alloys

Relationship between relaxation embrittlement and atomic cluster structure was explored by simulation and experimental methods for two amorphous alloys: Zr60Cu30Al10 and Zr50Cu40Al10 (referred to as Zr60 and Zr50, respectively). Simulation results from large-scale molecular dynamics revealed that the Zr50 alloy exhibited a higher content of icosahedral clusters, which increased more obvious during the quenching process compared to the Zr60 alloy. As icosahedral clusters exhibit brittleness similar to quasicrystalline structures, we predicted that the Zr50 alloy would have a higher glass transition temperature Tg and more pronounced relaxation-induced brittleness than the Zr60 alloy based on this observation. To validate the predictions, experimental results confirmed the occurrence of relaxation brittleness in Zr50 and relaxation non-brittleness in Zr60, consistent with the XRD analysis and electron microscope-based three-dimensional reconstruction in terms of icosahedral clusters. The agreement between the simulation calculations and the experimental data provides a reference for understanding the mechanism of relaxation embrittlement in amorphous alloys.

Effect of hyperfine structure on crystallization, microstructure and magnetic properties of amorphous Nd9Fe85B6 alloy

Crystallization of amorphous alloy is a commonly used method to fabricate nanocomposite permanent magnets. However, the effect of the hyperfine structures of amorphous alloy on microstructure evolution and magnetic properties of the obtained nanocomposites is far from understood. Here, amorphous Nd9Fe85B6 alloys with different hyperfine structures, i.e., different short-range orders (Rs = 0.80–0.91 nm), were prepared via melt spinning. The effects of the hyperfine structure on crystallization behavior, microstructure, and magnetic properties of the material upon thermal annealing were investigated in depth. Crystallization kinetics calculations show that a larger Rs leads to a smaller apparent crystallization activation energy, which leads to higher volume fractions of α-Fe and Nd2Fe14B. At the same time, a crystallizaition process dependent stage crystallization activation energy of Nd2Fe14B has been obtained, which is low at nucleation stage and increases with crystallization process, i.e. easy for nucleation but hard for growth, which leads to a smaller grain size of Nd2Fe14B. As a result, optimized magnetic properties were obtained in the sample with Rs = 0.91 nm.

Relationship among intrinsic magnetic parameters and structure and crucial effect of metastable Fe3B phase in Fe-metalloid amorphous alloys

The intrinsic heterogeneity of an amorphous structure originates from composition, and the structure determines the magnetic properties and crystallization models of amorphous magnets. Based on classical Fe–B binary magnetic amorphous alloys, the relationship between the structure and magnetic properties was extensively studied. The stacking structure of Fe–B binary amorphous alloys exhibit discontinuous changes within the range of 74–87 at.% Fe. The structural feature can be expressed as Amor. Fe3B matrix + Fe atoms are transforming into Amor. Fe matrix + B atoms with the increase of Fe content. The solute atoms are uniformly distributed in the amorphous matrix holes, similar to a single-phase solid solution structure. The transition point corresponds to the eutectic crystallization model composition (Fe82B18 to Fe83B17). A high Fe content will amplify magnetic moment sensitivity to temperature. Under a given service temperature, the disturbance effect of magnetic moment self-spinning will offset the beneficial effect of increasing Fe content and induce the saturation magnetization (Ms) value to decrease. Binary amorphous Fe–B alloys obtain the maximum Curie temperature near 75 at.% Fe, which is slightly smaller than that of the corresponding metastable Fe3B phase, i.e., the amorphous short-range order structure maintains the highest similarity to the Fe3B phase. The chemical short-range ordering (SRO) structure of amorphous alloys exhibits heredity to corresponding (meta)stable crystal phases. The unique spatial orientation structure of the metastable Fe3B phase is the structural origin of the amorphous nature. This study can guide the composition design of Fe-metalloid magnetic amorphous alloys. The design of materials with excellent magnetic properties originates from a deep understanding of precise composition control and temperature disturbance mechanism.

Effects of a small amount of B addition on the geometric structure, electronic structure and magnetic properties of FePC amorphous alloys

The saturation magnetization of Fe-based amorphous alloys can be effectively increased by adding a small amount of metalloid B. In this paper, the influence mechanism of a small amount of B on the geometric structure, electronic structure and magnetic properties of Fe80P12-xC8Bx (x = 0, 1, 2, 3, 4) amorphous alloys was investigated by using first-principles molecular dynamics simulations. The addition of B does not significantly change the distribution of Voronoi polyhedra with Fe as the center but increases the number of Fe atoms in the vicinity of Fe. The B atom with a small radius easily diffuses to the space between atoms, which increases the density of the Fe-based amorphous alloy and the aggregation among Fe atoms, thus enhancing the interaction between Fe atoms and finally increasing the saturation magnetization of the amorphous alloy. This provides an effective way to develop amorphous alloys with excellent magnetic properties.

Mesoporous Ru(Co, Ni)B bimetallic amorphous alloy for CO2 hydrogenation to formic acid

Amorphous metal alloy catalysts have attracted even-increasing attention owing to their high activity and selectivity. However, they are mainly prepared in ultrafine nanoparticles, which are easily gathered and challenging to separate. In this work, mesoporous Ru(Co, Ni)B bimetallic amorphous alloy catalysts with magnetic properties that can be easily recovered were synthesized via surfactant self-assembly. The as-prepared Ru1%CoB catalyst exhibited 578 μmol/g/h production rate and 99% selectivity to HCOOH during liquid phase CO2 hydrogenation owing to the unique amorphous alloy structure corresponding to the well-distributed, coordination-unsaturated, electron-enriched and synergistic active sites, which promoted the adsorption, activation, dissociation, and surface reaction of CO2 and H2. Moreover, the mesoporous channels also promoted the diffusion and adsorption of CO2 and H2. Besides, the Ru1%CoB catalyst also displayed good durability in CO2 hydrogenation owing to the robust stability against the crystallization of amorphous alloy, the collapse of mesopores, and the leaching of active sites.

Change in the Radius of the First Coordination Sphere in Amorphous Alloys during Deformation

Changes in the structure of amorphous alloys under deformation by high-pressure torsion, multiple-pass rolling, and pressure treatment have been studied using X-ray diffraction and scanning electron microscopy. It has been shown that under all types of deformation, shear bands are formed in amorphous alloys, which are regions of lower density compared to a surrounding undeformed amorphous matrix. Shear bands are regions of an increased free volume; the formation of bands results in steps occurring on the surface of samples. The number of shear bands and the surface morphology of deformed amorphous alloys are determined by the deformation type and physical properties of a material.

Structure and physical properties changes of Fe-based amorphous alloy induced by Joule-heating

Structure and physical properties changes of Fe-based amorphous alloy induced by Joule-heating

Local atomic configurations in mechanically alloyed amorphous (FeCoNi)70Ti10B20 powders

The atomic structure of amorphous (FeCoNi)70Ti10B20 alloy synthesized by mechanical alloying was investigated using high energy synchrotron X-ray diffraction and inverse Monte Carlo simulations of pair distribution functions. Empirical potential structure refinement indicates a chemical short-range order at the length scales of 2.1–2.5 Å via local atomic arrangements forming deformed bcc-like clusters. The structural model obtained was described by bond lengths, coordination numbers, and bond angle distribution functions determined for the first neighbor atoms by x-ray scattering supplemented with 3D Monte Carlo simulations.

Dynamic relaxation behavior and its effect on mechanical properties of FePBCCu amorphous alloy

The correlation between the dynamic relaxation behavior and micro-inhomogeneous structure of amorphous alloy is of significance for exploring the mechanical deformation. In this work, we report the pronounced secondary (β) relaxation process in FeP(B)CCu amorphous alloys with different microstructures, which reveals the local heterogeneity at atomic scale. With the help of thermodynamic analysis, it was found that compared to the partially crystallized alloy, the more local structural heterogeneities were activated in the amorphous matrix due to the low activation energy of β relaxation and the high activation energy of crystallization. Physical aging far below the crystallization temperature demonstrated that atomic rearrangement supported the weakening of β relaxation amplitude as well as the increment of storage modulus, especially for FePBCCu amorphous alloy, which was consistent well with the increases of the reduced modulus and hardness by nanoindentation tests. Moreover, the fitted results from the Maxwell-Voigt model on creep curves revealed that the diffusion and rearrangement of atoms in loosely packed zones corresponding to the β relaxation were more active during aging. Our findings provide new insight into understanding the dynamic relaxation behavior in FePBCCu amorphous alloy and render it an ideal system to probe the correlation between relaxation and mechanical deformation.

Changes in the Structure of Amorphous Alloys under Deformation by High-Pressure Torsion and Multiple Rolling.

X-ray diffraction and scanning electron microscopy were used to study changes in the structure of amorphous alloys under deformation by high-pressure torsion and multiple rolling. The change in mean nearest neighbor distance (the radius of the first coordination sphere) under deformation was determined. During deformation, shear bands are formed in amorphous alloys, which are regions of lower density compared to the surrounding undeformed amorphous matrix. Shear bands are zones of increased free volume, in which crystallization processes are facilitated. The change in the proportion of free volume under deformation of various types was estimated. The formation of shear bands leads to the appearance of steps on the surface of the samples. The number of shear bands and the surface morphology of deformed amorphous alloys were determined by the type of deformation and the physical properties of the material. The results obtained are discussed within the concept of free volume in the amorphous phase.

Advanced structure research methods of amorphous Co69Fe4Cr4Si12B11 microwires with giant magnetoimpedance effect: Part 2 – Microstructural evolution and electrical resistivity change during DC Joule heating

This Part 2 focuses on the processes of atomic regions ordering of the amorphous material and continues study of the processes occurring in Part 1. The formation of pre-crystals / clusters and nanocrystallization of Co-based amorphous microwires during DC Joule heating were investigated, as well as the influence of these processes on the electrical resistance of the samples and the effect of giant magnetoimpedance (GMI). In this paper we investigated the dependence of the change in the maximum response of the GMI diagonal component at different temperatures and holding times in the DC Joule heating process, and discuss the effect of the ductile-brittle transition on the electrical resistance and the GMI effect. Using high-resolution transmission electron microscopy (HR-TEM) and the inverse Fourier transform technique, it was shown that at long exposure during the DC Joule heating, significantly below the crystallization temperature (~ 400 °C), the formation and growth of pre-crystals / clusters occur in various sizes (1 – 8 nm) and shapes. At the initial stage of crystallization, the microwire has three distinct regions of the clusters and nanocrystals formation (surface, pre-surface, and bulk). Moreover, pre-crystals / clusters growth and further bulk formation of nanocrystals (of 10 nm and more) leads to a sharp drop in the electrical resistance and degradation of the GMI microwire diagonal component response. The approach of controlled long-term holding during the DC Joule heating applied in the study allows for creation of various nanoscale structures in an amorphous matrix and provides an opportunity to grow of a given structure in amorphous alloys.

Production conditions and fine structure parameters of metallic glasses based on light rare-earth elements

Thermal regimes of formation and parameters of the fine structure of amorphous alloys based on light rare-earth elements (E-La, Ce, Pr) with normal metals (M-Al, Cu, Ag) obtained by rapid cooling of melt layers on the inner surface of a rotating cylindrical heat receiver are studied. It has been shown that the alloys under study belong to materials with an average level of glass-forming ability (GFA), whichsolidify without crystallization in cross sections from 35 to 65 μm during quenching from a liquid state. Based on the correlation between the sizes of coherent scattering regions and the shortest interatomic distances found by X-ray diffraction for E-M amorphous alloys with the corresponding characteristics of metallic glasses of other classes, a conclusion was made about a close analogy of the atomic structure of noncrystalline phases fixed by quenching metallic melts.

Effects of B substitution for P on structure and magnetic properties of FePB amorphous alloys by first-principle investigation

Effects of the substitution of B for P on structure and magnetic properties of FePB amorphous alloys are investigated by first-principle molecular dynamics. Our analysis shows that Fe-centered polyhedra are mainly distorted icosahedral structures, and P- or B-centered polyhedra are mainly icosahedrons and triangular prisms. It is found that Fe80P5B15 amorphous alloy has the most 15xx bond pairs and higher local five-fold symmetry. With the increase of B atoms, magnetic moment of the amorphous alloy gradually increases, which is in good agreement with the experiments. Due to higher local symmetry, Fe80P5B15 amorphous alloy produces a larger splitting exchange energy and hence a higher magnetic moment. Fe atoms are easy to lose electrons to be positively charged, but B or P atoms are easily to gain electrons and are negatively charged. In addition, on account of the small radius of B atoms, more Fe atoms are aggregated locally in Fe80P5B15 amorphous alloy. The more the number of neighboring Fe atoms, the largrer the magnetic moment of Fe atoms is, which makes magnetic moment in amorphous alloys gradually increases. These findings provide intentional guidance for the development of new soft magnetic materials.