Amorphous Metallic Alloys Research Articles

Electrochemical Properties of Ternary Amorphous Alloys Based on Iron and Cobalt in Alkali Solutions

We study the electrochemical behavior of Fe80Si6B14, Co72Si18B10, and Fe84Nb2B14 amorphous metal alloys based on Fe and Сo in alkali solutions of different concentrations. The protective oxide layers on Fe80Si6B14 electrodes have lower degrees of corrosion protection than for the Co72Si18B10 electrodes. Niobium clusters in the Fe84Nb2B14 alloy are reactive, which results in the rapid initial interaction of the electrode with a 1 М aqueous solution of KОН, which is retarded under the conditions of long-term contact with ions of the electrolyte. The Fe80Si6B14 and Fe84Nb2B14 alloys are characterized by a similar electrochemical behavior in 1 M and 5 М aqueous solution of KOH under the conditions of cyclic polarization of samples in corrosive media. As a result of fivefold scanning of the potential, it is shown that the electrochemical properties of the electrodes made of amorphous metallic alloys depend on the electrolyte concentration.

Production of Bulk Metallic Glasses by Ultrasonic Welding of Nickel Based Amorphous Ribbons

With the evolution of society new materials or classes of materials must be developed. The metallic alloys with amorphous structure have exceptional physical properties due to the spatial order of the atoms in structure and the absence of crystalline defects such as dislocations, grain boundaries, etc. Due to the metastable states in which these alloys are located, obtaining bulk materials from amorphous metal alloys is difficult, being limited to simple geometries and high production cost. This problem can be solved by using the ultrasonic welding of amorphous ribbons for the production of bulk metallic glasses.In this paper, we aimed to produce bulk metallic glasses materials by welding the ribbon packages in ultrasonic field. In order to prove the preservation of the amorphous structure of both the primary welding alloys as well as after the welding of the amorphous ribbons, Differential thermal analysis (DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM) analysis were carried out. Vickers micro-hardness test was also performed in order to reveal the mechanical properties in the welded joint.

Experimental analysis on the quality aspects of micro-channels in mechanical micro milling of Zr-based bulk metallic glass

Amorphous metallic alloys possess important properties that are suitable for making micro-components used in several micro applications. Geometric accuracy in the shape and surface roughness of these micro components plays a vital role in their performance. In the present work, an experimental characterization of the quality aspects in the micro milling process is undertaken to assess the process capability in achieving the surface quality and the accuracy of the micro channels done on a workpiece made of bulk metallic glass. The influence of the cutting parameters on the quality aspects of the micro channels is investigated. The quality aspects analyzed are the average width of the micro channels and the surface roughness of the base of the micro channels. The results reveal that the average width of the micro-channels decreases with the increase in the axial depth of cut. For the chosen range of feed rates, higher feed rate shows better control towards the desired value. It is found that the effect of the feed per tooth on the roughness parameters is significant. In the present study it is observed that the surface roughness decreases with the decrease in the feed rate at values greater than the average cutting edge radius and reaches a minimum, and then tends to increase with further reduction in the feed rate. At very low feed rates the increase in the surface roughness values with the decrease in the feed rate is attributed to the material side flow that occurs at the secondary cutting edge.

Current Review on the Research Status of Cemented Carbide Brazing: Filler Materials and Mechanical Properties

Cemented carbides have been widely applied in cutting tools and wear-resistant components due to their ultrahigh hardness and good wear resistance. However, the disadvantages of limited impact toughness and high cost have restricted their further application. Consequently, cemented carbides are usually joining with ductile steels to combine the advantages of both. Among various materials joining technologies, brazing have been an effective method to achieve high quality dissimilar cemented carbide joints. In this paper, the research status of cemented carbide brazing is reviewed. The materials utilized as brazing filler metal in cemented carbide brazing joints are summarized in detail. Researchers have done lots of works utilizing Cu based and Ag based brazing filler metals which are the most commonly used interlayers in brazed joints of cemented carbide and ductile steel. The effects of different filler metal on wettability, microstructure, phase constitution and mechanical properties of brazed cemented carbides joints are analysed. Besides, a series of newly developed brazing filler material such as nickel-based high temperature brazing filler metal, amorphous brazing filler metal and high entropy alloy brazing filler materials are also involved. These newly developed brazing filler metals have shown great potential in fabricating high quality joints. Finally, the current issues of cemented carbide brazing are reviewed and the develop trend is predicted.

Electrochemical properties of amorphous metal alloys of Al-(Gd, Y)-Ni system in alkaline solution

The study of the chemical activity of amorphous Al-Ni metal alloys with various additives determines the feasibility of their operation in various fields of technology. This is a pressing scientific and applied problem, therefore, there is a need for electrochemical study of oxide-hydroxide films on the surface of amorphous alloys with variable composition of alloying elements, such as yttrium and gadolinium in 0.5‑5.0 M KOH aqueous solutions. The self-determination of the electrode potential of the AMA electrodes, ie without external influences, in particular polarization, was investigated potentiometrically. It is found that the introduction of nickel and RE stabilizes the corrosion resistance of aluminum alloys in alkaline environments, and the nature of RE practically does not affect the stable value of the potential of AMA electrodes, the value of which ranges from ‑0.75 to ‑0.79 V. Potentodynamic conditions produced polarization curves, which were the basis for studying the features of electrochemical processes on the surfaces of the studied materials in different media. A tenfold polarization of the AMA ‑ electrode into the region of positive potentials was performed. The anode polarization time was 540 s. AMA‑electrodes were polarized in aqueous KOH solutions of different concentrations. Electrochemical transformation of AMA electrodes in media of different concentration of KOH solution from 0.5 to 5 M was investigated by voltammetric analysis at their polarization within the potentials from ‑1.7 to + 1.0V. It is shown that yttrium doping reduces the passivity of the alloy surface, especially in 5 M KOH, and the replacement of yttrium by gadolinium, the combined presence of yttrium and gadolinium stabilizes the corrosion properties within concentrations from 1.0 to 5.0 M, in particular, the corrosion potentials acquire stable values. and ten ‑0.75 ± 0.05 V. It is shown that Y doping reduces the passivity of the alloy surface, especially in 5 M KOH, and the replacement of Y with Gd, the combined presence of Y and Gd stabilizes the corrosion properties within concentrations from 1.0 to 5.0 M, in particular, the corrosion potentials become stable. Values within the range from -0.75 to -0.78 V. However, due to the tenfold polarization of the AMA electrodes within the potentials from -1.7 to + 1.0 V, the corrosion potentials of the Al 87 Ni 8 Y 5 and Al 87 Ni 8 Gd 5 AMAs in the cathodic side shift approximately 0.03 V. Keywords: amorphous metal alloys, corrosion resistance, rare earth metals, aluminium.

Behaviour of Metallic Glasses under Local Loading and after External Action

Abstract—To determine the cracking susceptibility for amorphous metal alloys (AMAs) or metallic glasses, a method based on the determining the dependence of the relative crack resistance (χ) on the load applied to intender of PMT-3 microhardness tester is proposed. In the method, the relative crack resistance at a load of 160 g is set equal to unit. At lower loads, crack resistance has been determined as the average of 10 measurements. In this article, we also have proposed a method for determining the heating temperature of AMA ribbons during laser beam machining that is based on a comparison of the dependence of the relative crack resistance of AMAs on load applied to indenter for samples annealed in the furnace and after laser irradiation. It has been found that cracks begin to appear in the samples after a ten-minute annealing at Т = 773 K. Fatigue tests of samples under a load varying from a maximum value of 750 MPa to a minimum of 400 MPa under a condition of repeated stress cycle with a frequency of 2 Hz have been carried out using a specially designed setup. In the domain exposed to laser radiation, four characteristic areas can be distinguished on the sample surface: internal reflow zone; dendritic growth area; area with unfinished growth of dendrites, area not exposed to radiation. In these areas, the relative crack resistance (χ) determined via the critical stress intensity factor of the first kind K1c monotonically decreases from 1 in the center to 0 at the periphery. It has been established that the laser action does not affect fatigue, the fatigue limit of the samples remains the same and is equal to 428 MPa. The characteristic features of the destruction are revealed. Cracks that propagate with branching in the reflow zone and after passing through its boundary develop rectilinearly have been found.

High-Performance Metallic Amorphous Magnetic Flake-Based Magnetodielectric Inductors

Flake-shaped FeSi-based metallic amorphous alloy particles, having an aspect ratio as high as 175 to 1, were prepared by ball milling gas atomized amorphous powders of an effective diameter of 20 micrometers. The starting powder had a saturation magnetic flux density, Bs, of 1.5 T and a coercivity, Hc, of 94 A/m. The aspect ratio of the flakes, as well as their magnetic properties, were controlled by milling process parameters, such as duration, speed, and the type, mass and diameter of the milling balls. To minimize the oxidation of the charge, the powders were handled in an argon gas-purged glove box, milled in toluene, and subsequently dried in vacuo. Subsequently, soft magnetodielectric composites were prepared by suspending and aligning the FeSi-based powders in paraffin wax or epoxy resin. The composites were then pressed into toroids for measurements of their high frequency complex permeability by a vector network analyzer. The influence of the flake aspect ratio and volume loading fraction on the permeability of the composites were investigated. Results indicate that the composite permeability increases with the flake aspect ratio. For example, for a given loading factor of 30 vol.%, the composite permeability at 0.1 GHz nearly tripled and approached the value of 10 by increasing the aspect ratio of the FeSi-based inclusions from 1 (spheres) to greater than 175 to 1 (flakes).

Porosity Determination and Characterization of Binder Jet Printed Structural Amorphous Metal (SAM) Alloy Parts Using X-Ray CT

Porosity Determination and Characterization of Binder Jet Printed Structural Amorphous Metal (SAM) Alloy Parts Using X-Ray CT

Low-Iridium-Content IrNiTa Metallic Glass Films as Intrinsically Active Catalysts for Hydrogen Evolution Reaction.

Although various catalytic materials have emerged for hydrogen evolution reaction (HER), it remains crucial to develop intrinsically effective catalysts with minimum uses of expensive and scarce precious metals. Metallic glasses (MGs) or amorphous alloys show up as attractive HER catalysts, but have so far limited to material forms and compositions that result in high precious-metal loadings. Here, an Ir25 Ni33 Ta42 MG nanofilm exhibiting high intrinsic activity and superior stability at an ultralow Ir loading of 8.14 µg cm-2 for HER in 0.5 m H2 SO4 is reported. With an overpotential of 99 mV for a current density of 10 mA cm-2 , a small Tafel slope of 35 mV dec-1 , and high turnover frequencies of 1.76 and 19.3 H2 s-1 at 50 and 100 mV overpotentials, the glassy film is among the most intrinsically active HER catalysts, outcompetes any reported MG, representative sulfides, and phosphides, and compares favorably with other precious-metal-containing catalysts. The outstanding HER performance of the Ir25 Ni33 Ta42 MG film is attributed to the synergistic effect of the novel alloy system and amorphous structure, which may inspire the development of multicomponent alloys for heterogeneous catalysis.

Hydrogen-induced softening and hardening of Zr-based amorphous alloy: dependence on the hydrogen content and mobility

The effects of hydrogen addition on the structural and mechanical properties of Zr57Al10Cu15.4Ni12.6Nb5 amorphous metallic alloy were analysed. Structural investigation, using x-ray diffraction, revealed that hydrogen addition causes the development of large void and structural expansion. By means of nanoindentation tests, it has been shown that hydrogen addition can induce either softening or hardening of Zr-based amorphous alloys depending on the extent of the hydrogen content and mobility. The shear softening of amorphous material is due to the weakness of atomic cohesion attributed to the squeezing of ‘mobile’ hydrogen atoms. When hydrogen content grows excessive, strongly bounded ‘immobile’ atoms form a densely packed structure that restrict the local atomic movement and consequently harden the amorphous material alloy.

A machine-learning approach to predicting and understanding the properties of amorphous metallic alloys

There is a pressing need to shorten the development period for new materials possessing desired properties. For example, bulk metallic glasses (BMGs) are a unique class of alloy materials utilized in a wide variety of applications due to their attractive physical properties. However, the lack of predictive tools for uncovering the relationships between BMGs' alloy composition and desired properties limits the further application of these materials. In this study, a machine-learning (ML) approach was developed, based on a dataset of 6471 alloys, to enable the construction of a predictive ML model to describe the glass-forming ability and elastic moduli of BMGs. The model's predictions of unseen data were found to be in good agreement with most experimental values. Consequently, we determined that an alloy with a large critical-casting diameter would likely have a high mixing entropy, a high thermal conductivity, and a mixing enthalpy of approximately −28 kJ/mol, and that a BMG with a small average atomic volume would likely have a high elastic modulus. The efficacy of ML was demonstrated in furnishing a mechanistic understanding and enabling the prediction of metallic-glass properties.

What should the density of amorphous solids be?

A survey of published literature reveals a difference in the density of amorphous and crystalline solids (organic and inorganic) on the order of 10%-15%, whereas for metallic alloys, it is found to be typically less than 5%. Standard geometric models of atomic packing can account for the polymeric and inorganic glasses without requiring changes in interatomic separations (bond lengths). By contrast, the relatively small difference in density between crystalline and glassy metals (and metallic alloys) implies variations in interatomic separations due to merging orbitals giving rise to reduced atomic volumes. To test this hypothesis, quantum density functional theory computations were carried out on ordered and irregular clusters of aluminum. The results point to decreasing interatomic distances with decreasing coordination, from which one can deduce that the geometrical method of random hard sphere packing significantly underestimates the densities of amorphous metallic alloys.

Modeling of Top Burr Formation in Micro-End Milling of Zr-Based Bulk Metallic Glass

Abstract In this study, an analysis is presented for the formulation of a model in top burr formation to estimate the width of the top burrs formed in micro-end milling process. In this analysis, the width of the top burrs, considered to be the measure of burr size of top burrs, represents the extent of burr formation. The model is applied to quantify the burr formation in Zr-based bulk metallic glass, an amorphous metallic alloy. In this study, micromilling experiments were carried out on the bulk metallic glass work material at different levels of feed rate, axial depth of cut, and cutting speed to compare the experimental values of top burr width with the predicted values. Analysis is carried out to characterize top burr formation based on the experimental results of burr sizes in the up-milling and down-milling side edges, and the influential effects of the cutting parameters on the burr formation are analyzed.

Influence of Focused Pulsed Laser Radiation on the Properties of Amorphous FeSi6B16 Metal Alloy

The effect of focused pulsed laser radiation (number of pulses and power density) on an amorphous FeSi6B16 metal film is studied. The states of the alloy before and after laser irradiation are analyzed using methods of atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and microhardness measurements. Focused laser radiation in any exposure mode is established to cause high-temperature heating of the surface of an amorphous alloy in the irradiation zone. The result of such heating is melting of the material surface and propagation of the heat wave front from the strongly heated surface to its inner layers, which induces the redistribution of elements in the Fe–Si–B system, a change in the structure, and an increase in the microhardness.

Reentrant glass transition leading to ultrastable metallic glass

Abstract Polyamorphs are often observed in amorphous matters, and a representative example is the reentrant glass transition in colloid systems. For metallic amorphous alloys, however, the cases reported so far are limited to metallic glasses (MGs) that undergo electronic transitions under gigapascal applied pressure, or the presence of two liquids at the same composition. Here we report the first observation of a reentrant glass transition in MGs. This unusual reentrant glass transition transforms an MG from its as-quenched state (Glass I) to an ultrastable state (Glass II), mediated by the supercooled liquid of Glass I. Specifically, upon heating to above its glass transition temperature under ambient pressure, Glass I first transitions into its supercooled liquid, which then transforms into a new Glass II, accompanied by an exothermic peak in calorimetric scan, together with a precipitous drop in volume, electrical resistance and specific heat, as well as clear evidence of local structural ordering on the short-to-medium-range scale revealed via in-situ synchrotron X-ray scattering. Atomistic simulations indicate enhanced ordering of locally favored motifs to establish correlations in the medium range that resemble those in equilibrium crystalline compounds. The resulting lower-energy Glass II has its own glass transition temperature higher than that of Glass I by as much as 50 degrees. This route thus delivers a thermodynamically and kinetically ultrastable MG that can be easily retained to ambient conditions.

Magnetic properties and vibration characteristics of amorphous alloy strip and its combination

Although the cores made with amorphous metal alloy have lowered no-load losses compared with the orientation silicon steel cores, a high cost and noise level are inevitable because the magnetostriction for amorphous metal alloy strip is larger than the ordinary one. This study mainly focused on the experimental systems and methods for magnetic properties measurement, vibration characteristics and noise level of amorphous alloy strip and combinations. The vibration characteristics and noise level of amorphous alloy composite strip were also studied. The influence of the annealing process on magnetic energy, vibration characteristics and noise level of amorphous alloy core were analysed in detail as well. All the testing results and analysis above are helpful for the transformer manufacturers, and they can replace the expensive amorphous alloy metal strip with the combinations to reduce the noise and cost of the cores.

Specific Features of the Transition of Amorphous Al87REM5Ni8(Fe) Alloys Into the Crystalline State Under the Influence of Temperature

We determine the kinetic parameters of crystallization of amorphous metallic alloys based on aluminum doped with rare-earth metals (REM) by the method of differential scanning calorimetry. It is shown that the amorphous metallic alloys based on aluminum crystallize in three stages. By using the Kissinger, Avrami, and Ozawa models, we compute the energies of activation for the first stage of crystallization on the basis of the results of differential scanning calorimetry. It is shown that the Al–REM–Ni alloys are nanocrystallized by a kinetically controlled mechanism. The substitution of Gd for Y leads to a decrease in the temperature of nanocrystallization by 20–40°K. At the same time, the substitution of Dy for Y leads to an increase both in the temperature of nucleation and in the temperature of growth of nanocrystals. As a result of the addition of Fe to the composition of the alloy, the range of nanocrystallization shifts by about 100°K. According to the Matusite model, for constant temperatures of phase transitions, it is shown that the growth of nanocrystals in amorphous metallic alloys of the Al–REM–Ni system is realized in the 1D direction and linearly (interface control). In amorphous alloys, Dy substantially increases the temperatures of phase transitions and the number of atoms in clusters and decreases the microhardness.

Virtual bound states elements and their effects on magnetic and electrical properties of Fe-Ni based metal amorphous nanocomposites

Metal amorphous nanocomposite alloys, with compositions (Fe70Ni30)80-xNb4Si2B14TEx (0 ≤ x ≤ 5), where TE is a transition element, and (Fe70Ni30)80-yNb4+ySi2B14 (0.5 ≤ y ≤ 2) were synthesized. Samples were annealed at 440 °C and strain-annealed at 440 °C and 300 MPa. Resistivity was found to increase with small substitutions of TE elements. Increasing V resulted in reduced Bs from 1.2 T to 0.5 T. Further Mo additions lowered Bs to 0.6 T, and consistently reduced the permeability. For Cr and Nb, resistivity increased, and strain-annealed permeability was lower than the annealed permeability. Lastly, toroidal core losses on (Fe70Ni30)79.5Nb4Si2B14V1 yielded W1.0/400 = 2.1 W/kg, and W1.0/1 k = 6.0 W/kg.

Analysis of the atomic structure of the amorphous metal alloy Al84Ni6La10

The paper presents an analysis of the atomic radial distribution function of the amorphous metal alloy Al84Ni6La10 based on the fragmentary model. A comparative analysis of the most probable interatomic distances in the alloy and its compounds demonstrated the presence of crystalline nuclei of the following phases: Al3La, AlNi3, Al4La and Al. The crystalline nuclei of the Al4La compound are the smallest (~7-8 Å), while the minimal size of the most nuclei of the other phases is 1-1.5 nm. The following phases were observed in the crystallised alloy: Al11La3, Al3Ni, and Al.

Corrosion Resistance of Some Amorphous Metallic Fe–P–M (M = Si, Nb, Mo) Alloys: Effects of Composition, Structural Relaxation, Partial Crystallization, and Local Deformation

The corrosion resistance of metallic amorphous alloys (AAs) Fe80.2P17.1Mo2.7, Fe80.5P18.4Nb1.1, Fe98 –xPxSi2 (x = 14, 16, 20), Fe76.5P13.6Si4.8Mn2.4V0.2C2.5 in a 0.1 M solution of Na2SO4 (pH 6.25) and its change due to structural relaxation, nanocrystallization, and local deformation are studied. The activation of structural relaxation by photonic treatment is shown to increase the corrosion resistance of AAs. As the phosphorus content in the Fe98 ‒ xPxSi2 system decreases, the corrosion resistance of AAs decreases because of partial crystallization, which is accompanied by the formation of iron phosphides during rapid cooling of a melt, and silicon segregation at phase boundaries. The formation of local deformation zones in the near-surface layer of Fe76.5P13.6Si4.8Mn2.4V0.2C2.5 AA decreases its corrosion resistance. The niobium alloying of Fe‒P AAs is shown to be effective to decrease the corrosion rate.