Crystallization Of Amorphous Alloy Research Articles

Kinetics of crystallization and soft magnetic properties of Co72Fe8B10Si10 amorphous alloys

Co72Fe8B10Si10 amorphous alloy was prepared in an Ar atmosphere using a single roller rapid quenching technique at a wheel speed of 25 m/s. The prepared ribbons were annealed for 1 h at temperatures ranging from 473 to 773 K. X-ray diffractometer was used to observe the microstructure transformation. Field emission scanning electron micrographs exhibit mosaic type structures that become more prominent with increasing annealing temperature. Energy dispersive X-ray spectroscopy was also utilized to observe the concentrations of elements. The Kissinger and Ozawa equations were utilized to determine the amorphous alloy's crystallization activation energy. The two methods revealed consistent findings in their calculations. At 473 K, the obtained maximum real initial permeability (μ′max) is 376 which remains unchanged up to 10 kHz, whereas for 573 K, μ′max is noted to be 361 to 100 kHz. Other magnetic parameters such as loss factor, quality factor, and relative quality factor were also investigated for the Co72Fe8B10Si10 amorphous alloy to elucidate its suitability in such materials based devices.

Influence of Pulsed Interference Laser Heating on Crystallisation of Amorphous Fe77Cu1Si13B9 Ribbons.

Amorphous Fe77Cu1Si13B9 ribbons were treated with pulsed laser interference heating (PLIH). The research results will significantly contribute to a better understanding of the impact of PLIH on crystallisation and magnetic properties in precisely defined micro-areas of Fe77Cu1Si13B9 (FeCuSiB) ribbons, which has not yet been described in the literature. It was confirmed here that the use of the laser heating process allowed for the achievement of two-dimensional crystallised micro-areas, periodically distributed (at a distance of 17 µm) on the surface of the amorphous ribbons. The correlation between structural changes (SEM, TEM, HRTEM) and the distribution of magnetic field lines of heated amorphous Fe77Cu1Si13B9 ribbons is presented. Particular attention is paid to structural changes in micro-areas where, by controlling the laser interference heating process, the partial crystallisation of amorphous alloys and the formation of clusters or single nanocrystallites (α-Fe(Si)) embedded in an amorphous matrix occur. The addition of copper to the FeSiB alloy promoted the inhibition of grain growth. Electron holography of micro-areas confirmed shifts in the magnetic field lines in the areas of nanocrystallites, the presence of which in the structure caused the magnetisation of the surrounding amorphous matrix.

The Effect of a Coating on the Crystallization of Multicomponent Co-Based Amorphous Alloys

The effect of protective coatings on the crystallization of amorphous Co-based alloys was studied using the methods of X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The crystallization of the amorphous alloys was studied on as-prepared samples, deformed samples, and deformed samples with a protective coating. After heat treatment, the fraction of the crystalline phase in the pre-deformed samples was higher than in the undeformed samples. When using a protective coating, the fraction of nanocrystals formed during heat treatment increased. The size of the crystals formed in deformed samples was smaller, and in the deformed samples with a protective coating, they were slightly larger than in the corresponding initial samples. The reasons for the differences in the formed structure in the amorphous alloys under study are discussed in terms of free volume.

Oxide dependent textured crystallization on amorphous alloy surface

Amorphous alloys produced through rapid solidification offer a host of exceptional properties, with the caveat that achieving a fully amorphous structure. In our laboratory, the FeSiBPC alloy has demonstrated substantial industrial potential, but it contends with a persistent challenge in the form of surface crystallization during large-scale manufacturing. This study delves into the phenomenon of surface crystallization, variables influencing surface crystallization and elucidate its distinctive characteristics were studied. A noteworthy breakthrough emerges with the inaugural characterization of a high-quality fiber texture within an Fe-based amorphous alloy, achieved through Electron Backscattered Diffraction. Our findings underscore the remarkable sensitivity of air pressure within the chamber, revealing its significant impact on the intensity of Bragg peaks related to surface crystals. Moreover, the crucial role of an oxide atmosphere in effectively mitigating surface crystallization and offer insights into the mechanisms governing this preventive action. This study provides valuable insights into the intricate interplay of factors governing surface crystallization in amorphous alloys, offering promising avenues for enhanced industrial applications.

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.

The effect of crystalline structure on the mechanical behavior in Zr-based amorphous materials: A molecular dynamics simulation

The structure relaxation in the Zr-based amorphous phase affects the microstructure and mechanical properties of metallic glasses. To clarify the mechanical properties and deformation mechanism of amorphous crystallization, the compression and tensile deformation of the Zr90Cu10 amorphous model with different levels of ordered lattice structure were studied by molecular dynamics simulation. The influence mechanism of crystals on the deformation and mechanical properties of amorphous alloys was investigated using atomic-scale stress‒strain curves, atomic structures, and dislocation line distributions. The results show that the in situ crystallization of amorphous alloys has a positive effect on enhancing the elastic modulus and yield strength of amorphous metals. The high-stress regions in the model are predominantly concentrated within the amorphous phase. The phase dislocation entanglement under stress will improve the plasticity of the amorphous state. This work also discusses the deformation mechanism of nanocrystalline amorphous alloys at the atomic level.

Solute atom mediated crystallization of amorphous alloys

We propose a new mechanism of crystallization of amorphous alloy which is mediated by additional solute atoms produced by electronic excitation. For a freestanding Pd-19at%Si amorphous alloy film, electron irradiation causes subtle structural change. By contrast, extensive crystallization of Pd-19at%Si amorphous alloy sandwiched by amorphous (a-) SiOx films, i.e., a-SiOx/a-Pd-Si/a-SiOx, occurred by 75 keV and 200 keV electron irradiation. This crystallization was induced by irradiation not only at room temperature but also even at 90 K. It should be emphasized that the crystallization can be realized by 75 keV irradiation at 90 K via the electronic excitation; where both knock-on damage and a possible thermal crystallization can be excluded. A resultant product of the crystallization after electronic excitation (i.e., electron irradiation), hexagonal Pd2Si, differs from that of thermal annealing (orthorhombic Pd3Si). Evidence for decomposition of a-SiOx by electronic excitation contributes essentially to the crystallization of the a-Pd-Si in the composite film has been obtained in this study. Supply of dissociated Si to the a-Pd-Si layer may cause instability of the amorphous phase, which serves as the trigger for the remarkable structural change; i.e., additional solute atom mediated crystallization.

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.

NOVEL FUNCTIONAL MATERIALS BASED ON AMORPHOUS ALLOYS OF Fe–Сo–Сr SYSTEM

The work is devoted to the study of the possibility of obtaining hard magnetic materials during the crystalli-zation of amorphous alloys of the Fe–Co–Cr–B–Si system. The influence of boron content in alloys on their glass-forming ability was analyzed. The structure and phase transformations in alloys during heating were ana-lyzed using X-ray diffraction and transmission electron microscopy. Influence of the phase composition on the magnetic properties of the alloys has been established. It is shown that the formation of a nanosized eutectic structure [α + (Fe, Cr)3B] during the crystallization of an amorphous matrix is promising for development of new hard magnetic materials.

Deformation Mechanism of Depositing Amorphous Cu-Ta Alloy Film via Nanoindentation Test.

As a representative of immiscible alloy systems, the Cu-Ta system was the research topic because of its potential application in industry, military and defense fields. In this study, an amorphous Cu-Ta alloy film was manufactured through magnetron sputter deposition, which was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties of Cu-Ta film were detected by the nanoindentation method, which show that the elastic modulus of Cu3.5Ta96.5 is 156.7 GPa, and the hardness is 14.4 GPa. The nanoindentation process was also simulated by molecular dynamic simulation to indicate the deformation mechanism during the load-unload stage. The simulation results show that the structure <0,2,8,4> and <0,2,8,5> Voronoi cells decreased by 0.1% at 50 Ps and then remained at this value during the nanoindentation process. In addition, the number of dislocations vary rapidly with the depth between indenter and surface. Based on the experimental and simulation results, the Voronoi structural changes and dislocation motions are the key reasons for the crystallization of amorphous alloys when loads are applied.

&lt;i&gt;In situ&lt;/i&gt; study of heterogeneous media combustion processes by time Resolved XRD

The use of in situ diagnostic methods is required to obtain data on the structure and composition of the material in real time when studying condensed substances in the course of chemical reactions and phase transformations. We present the results on the development and application of the time-resolved X-ray diffraction method for the diagnosis of fast processes in heterogeneous condensed media, including self-propagating high-temperature synthesis. An X-ray tube was used as a radiation source. The method is based on the use of high-speed registration of XRD patterns in a wide angular interval and provides obtaining in situ data on the evolution of the crystal structure of the reactants. A high-speed linear detector and reaction chambers, an effective analysis system with a time resolution in the range of 10–1 – 102 sec has been developed on the base of a powder diffractometer. A complex of object-oriented diffraction techniques has been developed to study the dynamics of phase transitions in self-propagating high-temperature synthesis of inorganic materials, combustion of energy systems and liquid solutions, crystallization of amorphous alloys, in the analysis of the phase composition of materials in the process of heat treatment. The results obtained can be used to identify the mechanism of structural and chemical transformations in condensed matter.

Тепловые свойства вещества в рамках модели двухфазной системы

It has been established that the relations of the two-phase system model are applicable for describing the thermal properties of solids with disordered and crystalline structures. It is shown that the model adequately describes the curves of isochronous and isothermal crys-tallization of amorphous alloys and thermal changes in the volume of their samples. It is also suitable for calculating the heat capacities and thermal expansion coefficients of sub-stances that are diverse in their physical nature.

Thermal properties of matter within the model of a two-phase system

It has been established that the relations of the two-phase system model are applicable for describing the thermal properties of solids with disordered and crystalline structures. It is shown that the model adequately describes the curves of isochronous and isothermal crys-tallization of amorphous alloys and thermal changes in the volume of their samples. It is also suitable for calculating the heat capacities and thermal expansion coefficients of sub-stances that are diverse in their physical nature. Keywords: two-phase system, thermal expansion coefficient, heat capacity, amorphous alloys, com-plex oxides.

Structure and magnetic properties of amorphous and nanocrystalline Co-Fe-B-(Nb, Ti) alloys

The structure and magnetic properties of amorphous and nanocrystalline Co56Fe16B20X8 (X=Nb, Ti) alloys have been studied by X-ray diffraction and vibrating sample magnetometry. It is shown that the saturation magnetization of the amorphous Co56Fe16B20Ti8 alloy is higher than that of the Co56Fe16B20Ti8 alloy. The temperature dependence of the saturation magnetization of amorphous alloys is measured and it is shown that the saturation magnetization of the Co56Fe16B20Ti8 alloy decreases with temperature more slowly than the magnetization of the Co56Fe16B20Nb8 alloy. Crystallization of amorphous alloys leads to a decrease in the saturation magnetization of both alloys. During crystallization, BCC nanocrystals are formed in the Co56Fe16B20Nb8 alloy and multiphase structure is formed in the Co56Fe16B20Ti8 alloy. Keywords: amorphous phase, crystallization, nanocrystals, magnetic properties.

Структура и магнитные свойства аморфных и нанокристаллических сплавов Co-Fe-B-(Nb, Ti)

The structure and magnetic properties of amorphous and nanocrystalline Co56Fe16B20X8 (X = Nb, Ti) alloys have been studied by X-ray diffraction and vibrating sample magnetometry. It is shown that the saturation magnetization of the amorphous Co56Fe16B20Ti8 alloy is higher than that of the Co56Fe16B20Nb8 alloy. The temperature dependence of the saturation magnetization of amorphous alloys is measured and it is shown that the saturation magnetization of the Co56Fe16B20Ti8 alloy decreases with temperature more slowly than the magnetization of the Co56Fe16B20Nb8 alloy. Crystallization of amorphous alloys leads to a decrease in the saturation magnetization of both alloys. During crystallization, BCC nanocrystals are formed in the Co56Fe16B20Nb8 alloy and multiphase structure is formed in the Co56Fe16B20Ti8 alloy.

Formation of bcc nanocrystals in Co-based amorphous alloys

The crystallization of amorphous alloys of Co-Fe-B-(Ti, Nb) system was studied by differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. It was determined that the alloying of amorphous alloys of Co-Fe-B system with elements having a bcc lattice promotes the formation of a metastable phase with this lattice during crystallization. Nanocrystal size and the fraction of the phase with a bcc lattice depend on the concentration of alloying components. When the concentration of bcc components increases, nanocrystal size decreases. When Nb (an element with a bcc lattice) is replaced by Ti (an element with an hcp lattice), the fraction of the bcc phase decreases, and multiphase crystallization (simultaneous formation of several crystalline phases) occurs. In Co56Fe16B20Ti8 alloy, the first crystallization stage consists of two steps. During the seemingly simultaneous formation of several crystalline phases, first a small quantity of the bcc phase and then Co23B6 and fcc-Cо crystals are formed sequentially. All the results obtained indicate heterogeneous nanocrystal formation with the nucleation on structurally related ordered regions (on ordered clusters which consist of alloy components with the structure related to the crystallizing phase).

A Non-Isokinetic Approach for Modeling Solid-State Transformations: Application to Crystallization of a Fe-B Amorphous Alloy.

Solid-state phase transformations like crystallization of amorphous alloys can be described by an analytical model incorporating a nucleation index a. However, this model cannot be used to examine isochronal transformations with abrupt changing of enthalpy differences performed with differential scanning calorimetry. Based on the model, a non-isokinetic approach is proposed and applied to analyze the isochronal crystallization kinetics of Fe85B15 amorphous alloy. The approach enabled us to obtain the kinetic parameters and activation energies for nucleation and growth.

X-ray Diffraction and Differential Scanning Calorimetry of the Crystallization of Amorphous Soft Magnetic Alloys Made of Naturally Doped Ferrophosphorus with One (P), Two (P, Si), and Three (P, Si, C) Amorphizers

The fraction of the amorphous phase remaining after the crystallization of amorphous alloys with one (P), two (P, Si) and three (P, Si, C) amorphizers is determined by X-ray diffraction. An increase in the fraction of a single-phase matrix is found to inhibit the crystallization during fast photon irradiation and heat treatment. Differential scanning calorimetry demonstrates that an increase in the number of amorphizers leads to a decrease in the crystallization rate of a structure, which is stable in an industrial atmosphere.

Single- and Multistage Crystallization of Amorphous Alloys

Single- and Multistage Crystallization of Amorphous Alloys

Anisotropic crystallization and magnetic properties of Fe-based amorphous alloys induced by ion inclined bombardment

The structures and magnetic properties of Fe73.5Si13.5B9Nb3Cu1 amorphous alloys after ion bombardment were investigated. The needle-like structure and granular structure nanocrystalline was respectively formed for the samples bombarded by ion beam at the incident angle of 75° and 90°, which was explained according to the crystallization and crystal growth under anisotropic stress produced by ion beam inclined bombardment. The ion beam inclined bombardment produced a compressive and parallel stress on the sample, the compressive stress promoted the nucleation by decreasing the critical nucleation free energy and the parallel stress caused the directional migration of atoms. Low incident angle ion bombardment only led to the structure relaxation, and high incident angle ion bombardment produced a large compressive stress on the sample, which then induced the crystallization of amorphous alloys. The anisotropic crystallization caused by ion beam inclined bombardment resulted in the increase of magnetic anisotropy and then improved the high-frequency properties.