Structure Of Amorphous Alloys Research Articles

The influence of annealing treatment on the electrocatalytic oxidation performance of Cu46Zr44·5Al7.5Gd2 amorphous alloy

The influences of annealing on the microstructure and the performance of electrocatalytic oxidation of Cu46Zr44·5Al7.5Gd2 amorphous alloy were investigated by operating heat treatment in the vacuum annealing furnace. It is found that structural relaxation occurred in the internal structure of amorphous alloy after annealing treatment, which will cause a significant effect on the relative electrochemical performance. Choosing annealing temperature of 300 °C and holding time of 20 min, hydrofluoric acid corrosion treatment was applied on the relaxation structural stage ribbons. According to cyclic voltammetry and chronoamperometry curve graphs, it is found that it has a high oxidation peak as an electrode, whose corresponding electric potential is −0.11 V and current density is 0.0187 A cm−2. After reusing the experimental samples for 20 cycles, the electrocatalytic oxidation property on methyl alcohol is found to gradually decline and then stabilize. At 1-5 experiment cycles, the effect of electrocatalyst is relatively good, which proves that the sample ribbons can be recycled.

Nanocrystallization and magnetic property improvement of Fe78Si9B13 amorphous alloys induced by magnetic field assisted nanosecond pulsed laser

The influence of the magnetic field (514 and 1642 Gauss) assisted nanosecond pulsed laser processing on the structure and magnetic property of Fe78Si9B13 amorphous alloy is analyzed in this paper. The magnetic field causes the surface to splash obviously, which is related to the Lorentz force generated by the applied magnetic field and current. The magnetic field assisted nanosecond pulsed laser does not cause the Fe78Si9B13 amorphous alloy to crystallize significantly, and the XRD pattern still shows a typical amorphous diffuse scattering peak. However, the magnetic field can enhance the crystallization sensitivity of the Fe78Si9B13 amorphous alloy, and make more nanocrystals formed in the heat affected zone based on the SAXS and TEM data. Moreover, the magnetic property of the Fe78Si9B13 amorphous alloy is improved when the magnetic field is 514 Gauss. The main reason is that the transition from fcc structure units to bcc structure units occurs in the amorphous alloy. When the applied magnetic field intensity is larger (1642 Gauss), the saturation magnetization decreases. It can be explained by the B content in the residual amorphous matrix is too high with the precipitation of α-Fe(Si) nanocrystals, which is not conducive to the increase of the saturation magnetization.

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.

Effects of annealing time on nanoscale structural heterogeneity and magnetic properties of Fe<sub>80</sub>Si<sub>9</sub>B<sub>10</sub>Cu<sub>1</sub> amorphous alloy

The evolution of nanoscale structural heterogeneity and its effect on magnetic properties of Fe<sub>80</sub>Si<sub>9</sub>B<sub>10</sub>Cu<sub>1</sub> amorphous alloy during structural relaxation after being annealed for different times are investigated in this work. The nanoscale structural heterogeneity is found to degenerate gradually with relaxation by using the small-angle X-ray scattering and atomic force microscope. Combined with Mössbauer spectroscopy analysis results, the enhanced comprehensive soft magnetic properties of the relaxed alloys can be attributed to the degeneration of nanoscale structural heterogeneity. From the flow unit model, the volume fraction of flow units decreases with relaxation proceeding, and some of the flow units annihilate and transform into the ideal elastic matrix. On the one hand, the relaxed sample with greater packing density has stronger magnetic exchange interaction and higher saturation magnetic flux intensity. On the other hand, the number density of quasi-dislocation dipoles decreases with the annihilation of flow units in the relaxation process, leading the pinning effect of the domain wall to be weakened. Consequently, the magnetic anisotropy decreases after relaxation, which results in the reduction of coercivity. In this work, the structural mechanism of the evolution of magnetic properties in the relaxation process of Fe<sub>80</sub>Si<sub>9</sub>B<sub>10</sub>Cu<sub>1</sub> amorphous alloy is investigated from the perspective of structural heterogeneity, which is helpful in establishing the correlation between the structure and magnetic properties of Fe-based amorphous alloys.

Evolution of the Zr42.5Сu42.5Al10Fe5 amorphous alloy structure during the HPT process

The paper analyzes the effect of severe plastic deformation on the structure, mechanical and thermal properties of a Zr42.5Сu42.5Al10Fe5 alloy. It was found that high pressure torsion induces phase separation of an amorphous matrix and causes formation of a complex structure containing nanocrystalline particles. The precipitation of nanocrystals leads to a change in the composition of the amorphous matrix and changes in the crystallization process and characteristic temperatures of the alloy. It is shown in the work that high pressure torsion significantly increases the hardness of the material, which is associated with the formation of nanocrystals in the structure and elastic stresses.

Surface and Structure of Amorphous Alloys after Pressure Treatment

Surface and Structure of Amorphous Alloys after Pressure Treatment

Observation of a Broadened Magnetocaloric Effect in Partially Crystallized Gd60Co40 Amorphous Alloy

To investigate the effect of crystallization treatment on the structure and magnetocaloric effect of Gd60Co40 amorphous alloy, the melt-spun ribbons were annealed at 513 K isothermally for 20, 40 and 60 min. The results indicate that, with increasing annealing time, the Gd4Co3 (space group P63/m) and Gd12Co7 (space group P21/c) phases precipitated from the amorphous precursor in sequence. In particular, in the samples annealed for 40 and 60 min, three successive magnetic transitions corresponding to the phases of Gd4Co3, Gd12Co7 and remaining amorphous matrix were detected, which induced an overlapped broadened profile of magnetic entropy change (|ΔSM|) versus temperature. Under magnetic field changing from 0 to 5 T, |ΔSM| values of 6.65 ± 0.1 kg−1·K−1 and 6.44 ± 0.1 J kg−1·K−1 in the temperature spans of 180–196 K and 177–196 K were obtained in ribbons annealed for 40 and 60 min, respectively. Compared with the fully amorphous alloy, the enhanced relative cooling power and flattened magnetocaloric effect of partially crystallized composites making them more suitable for the Ericsson thermodynamic cycle.

A novel amorphous alloy photocatalyst (NiB/In2O3) composite for sunlight-induced CO2 hydrogenation to HCOOH

Photocatalytic CO2 hydrogenation into fuels and value-added chemicals is considered as a promising strategy for CO2 conversion and utilization. However, the photocatalysts used usually displays low efficiency and poor durability. Herein we developed a novel catalyst by combining NiB amorphous alloy with In2O3 semiconductor, which exhibited very high HCOOH yield (5158.0 umol g−1 h−1) in CO2 hydrogenation under sunlight irradiation. The In2O3 acted as a photocatalyst for generating photoelectrons to reduce CO2 and provided sufficient surface hydroxyl (In−OH) groups favouring CO2 adsorption during the reaction. The high dispersion of NiB nanoparticles (co-catalyst) and interaction with In2O3 provided the rich interface between NiB and In2O3, favoring the surface reactions between CO2 and H2. Meanwhile, the unique amorphous alloy structure made the Ni electron-enriched, which promoted CO2 hydrogenation through the H2 dissociation. More importantly, the NiB amorphous alloy with good electric conductivity facilitated the transfer of photoelectrons from In2O3, which sufficiently diminished the photoelectron-hole recombination, leading to the enhanced quantum efficiency in photocatalytic CO2 hydrogenation.

Atomic arrangements in an amorphous CoFeB ribbon extracted via an analysis of radial distribution functions

We discuss the atomic structure of amorphous ferromagnetic FeCoB alloys, which are used widely in spintronics applications. Specifically, we obtain the pair-distribution functions for various atomic pairs based on high-energy x-ray diffraction data taken from an amorphous Co20Fe61B19 specimen. We start our reverse Monte Carlo cycles to determine the disordered structure with a two-phase model in which a small amount of cobalt is mixed with Fe23B6 as a second phase. The structure of the alloy is found to be heterogeneous, where the boron atoms drive disorder through the random occupation of the atomic network. Our analysis also indicates the presence of small cobalt clusters that are embedded in the iron matrix and percolating the latter throughout the structure. This morphology can explain the enhanced spin polarization observed in amorphous magnetic materials.

Amorphous alloys for electrocatalysis: The significant role of the amorphous alloy structure

Amorphous alloys for electrocatalysis: The significant role of the amorphous alloy structure

Unexpected effect of boron on magnetic properties and structure of amorphous Fe-rich FeSc alloys

Unexpected effect of boron on magnetic properties and structure of amorphous Fe-rich FeSc alloys

Atomic-level characterization of free volume in the structure of Cu67Zr33 amorphous alloy

The structure of Cu67Zr33 amorphous alloy was investigated in terms of packing density and free volume by using neutron, x-ray diffraction and reverse Monte Carlo (RMC) modelling. The RMC model was analysed by a method of decomposing the three-dimensional atomic configuration into fundamental polyhedral units (termed as ‘holes’ referencing the Bernal’s works) of which faces are all triangles consisting of chemical bonds. Not only tetrahedral and octahedral holes but also other larger holes were identified. Moreover, the atomic packing fractions and free volumes in the respective polyhedral holes were evaluated with reference to those for the corresponding crystal structures. The results show that the distribution of free volumes for the larger holes can be described by the exponential function assuming that there are no energetic interactions between each other. On the other hand, the local structural fluctuations due to densely and loosely packed tetrahedral holes were observed, leading to the negative free volume spaces.

The effect of the type of component crystal lattice on nanocrystal formation in Co-based amorphous alloys

The structure of Co-based amorphous alloys (Co-Fe-B-Si-M system, where M = Ni, Nb, or Mn) after initial stage of crystallization was studied. In Co67Fe5Nb8B20 alloy, the formation of a new metastable phase has been detected and its structure has been determined. The dependence of the type of the crystal lattice of nanocrystals being formed on the structure of an alloying component (Ni, Nb, or Mn) and their solubility in the main alloy component was discovered. The dependence observed agrees with the assumption of heterogeneous nanocrystal nucleation on ordered regions in the amorphous phase, which have the same short-range order as the crystalline phase being formed.

Amorphous Alloys Atomic Structure Investigation by Means of Electron Microscopy and Diffraction

In the paper, the atomic structure of amorphous and nanocrystalline alloys of the electrolytically obtained CoP, NiP, CoNiP, CoW, and CoNiW systems has been studied. The structure was investigated by electron microscopy and diffraction using a Libra 200 HR FE transmission electron microscope at an accelerating voltage of 200 kV within a temperature range of 50-35 °C. The obtained radial atom distribution function and the coordination sphere radii are in good agreement with the data for the cobalt structure in the cubic and hexagonal modifications. The high coordination numbers of the third and fourth coordination spheres allow suggesting a predominantly cubic structure of the local atom environment in CoP samples but somewhat lower, which is explained by the presence of free volume and phosphorus atoms distorting the local structure. When heating, the near atomic order also corresponds to the cubic phase of cobalt, and the ordering occurs in the second, third, and fourth coordination spheres. The data obtained for CoNiP alloys indicate that by configuration, the local atomic environment is closer to the hexagonal structure of nickel. In general, the structure of the CoP-CoNiP system alloy films obtained by electrolytic deposition is already in one of the local minima of the total system energy, which is confirmed by the near atomic order similar to the cubic phase of cobalt or hexagonal phase of nickel. This determines the good stability of the structure and properties during thermal exposure.

Direct observation of atomic-level fractal structure in a metallic glass membrane

Determination and conceptualization of atomic structures of metallic glasses or amorphous alloys remain a grand challenge. Structural models proposed for bulk metallic glasses are still controversial owing to experimental difficulties in directly imaging the atom positions in three-dimensional structures. With the advanced atomic-resolution imaging, here we directly observed the atomic arrangements in atomically thin metallic glassy membranes obtained by vapor deposition. The atomic packing in the amorphous membrane is shown to have a fractal characteristic, with the fractal dimension depending on the atomic density. Locally, the atomic configuration for the metallic glass membrane is composed of many types of polygons with the bonding angles concentrated on 45°–55°. The fractal atomic structure is consistent with the analysis by the percolation theory, and may account for the enhanced relaxation dynamics and the easiness of glass transition as reported for the thin metallic glassy films or glassy surface.

Restoration of the Structure of Amorphous Alloys and Partially Crystalline Alloys Using Cryogenic Thermocycling

The development of advanced technologies includes the development of new materials, which include composite amorphous nanocrystalline materials characterized by a unique combination of magnetic and mechanical properties (the latter include high strength, hardness, and wear resistance and others). However, the potential for using such materials is limited, since they are relatively quickly embrittled (lose their plasticity) even at room temperature. The properties of plasticity cannot be restored by heat treatment of the amorphous phase. It is found that properties of plasticity can be restored using thermal cycling in the interval between the temperature of liquid nitrogen (77 K) and room temperature (295 K). This process of treatment is called rejuvenation; it turns out to be acceptable only for bulk samples obtained in the form of rods. It is not suitable for samples in the form of ribbons with a thickness of 20–50 μm (the vast majority of amorphous alloys are obtained in this form). A modernized technology for treating such samples of amorphous alloys and partially crystalline alloys using cryogenic thermocycling is presented. This technology allows one to restore the amorphous structure and plasticity of thin ribbons. X-ray diffraction patterns of ribbon samples of alloy Al87Ni8Gd5 pre-annealed at a temperature of 170°C with the fraction of the nanocrystalline phase not exceeding 10% before and after several successive cooling/heating cycles show that the amorphous structure of the initial sample can be completely restored by increasing the number of cycles to two hundred.

Structural Heterogeneity of an Amorpous Nanocrystalline Alloy in the Nanometer Range

An approach to describe the structure of amorphous alloys obtained by fast quenching from a melt, based on the fluctuation theory of phase transitions, is proposed in t in such objects.

Correlation between the crystallized structure of Mg67Zn28Ca5 amorphous alloy and the corrosion behavior in simulated body fluid

The corrosion behavior of Mg-Zn-Ca amorphous alloys in simulated body fluid is of academic and engineering interests since they are potential biomaterials. The influence of the crystallized structure of the Mg67Zn28Ca5 amorphous alloy on the corrosion behavior in simulated body fluid (SBF) is investigated. The different crystallized structures were obtained by heating the amorphous sample to temperatures of 100 °C~300 °C. The results reveal that the amorphous Mg67Zn28Ca5 alloy shows better corrosion resistance in SBF than partially crystallized samples, and homogeneous chemical corrosion occurs on the surface of the amorphous alloy. In contrast, inhomogeneous galvanic corrosion occurs on the surfaces of the partially crystallized Mg67Zn28Ca5 sample; and the corroded surface becomes more rugged with increasing the crystallized temperature. The corrosion rate (Vcorr) of the Mg67Zn28Ca5 amorphous alloy in SBF shows a nearly linear relation with the crystallized volume fraction (CVF), i.e., Vcorr= −8.38+96.23CVF, indicating that its corrosion behavior is readily tuned by crystallization.

The forming and crystallization behaviors of Zr50Ti5Cu27Ni10Al8 bulk amorphous alloy by laser additive manufacturing

Due to the small size and serious crystallization, the wider application of amorphous alloy materials is limited. In this paper, the bulk amorphous alloy with the size of 15 mm × 15 mm × 12 mm was made by selective laser melting technology. The characters of the composition and structure of the as-prepared bulk amorphous alloy and the thermal effect of the preparation process were analyzed. The results showed that the cooling rate of both the molten pool and the heat affected zone were much higher than the critical cooling rate of the amorphous alloy and, therefore, the cooling rate was not the reason for the crystallization in this experiment. The molten pool of the formed amorphous alloy block was completely amorphous. Due to the accumulation of structural relaxation, crystallization occurred in the heat affected zone, but the amorphous structure was still dominant. The increase in deposition layer had no obvious effect on crystallization.