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The stability of high-entropy alloys, like equiatomic and non-equiatomic micro- and nanostructural ones, is relevant when creating stable multicomponent compositions with improved performance. The implementation of such materials is possible by mechanical alloying, magnetron sputtering, as well as by the electrochemical method using the «top-down and bottom-to-top» strategy at moderate temperatures < 200°C with controlled production of both micro-from 0,5 to 20 μm and nanoscale high-entropy alloys with particles from 2 to 10 nm. The well-studied «structure-property» relationship for classical alloys is not yet completely clear for nano-high-entropy alloys, but it is obvious that it is possible to form excellent mechanical characteristics by selecting chemical compositions and a special heat treatment regime. Regarding the chemical composition, requirements are imposed both on the main components and alloying additives. Preliminarily, not only compositions are selected, but also methods for the synthesis of high-entropy alloys, including ab initio (density functional theory), neural network prediction, and classical molecular dynamic simulation with possible conditions for the formation of model nano- high-entropy alloy samples, as well as derivative options. The resulting descriptions are compared with real methods of high-entropy alloys synthesis, for example, exposure to various synthetic media.

The principles of designing high-entropy alloys related to the selection of elements are analyzed. When selecting elements, a parametric approach is used, including chemical and topological parameters. The main chemical parameter is the enthalpy of mixing of elements, the main topological parameter is the atomic radius. It is emphasized that the use of modified atomic radii (which take into account the local electronic environment) better predicts the formation of either amorphous or crystalline high-entropy alloys. Four main effects that determine the properties of high-entropy alloys are considered: the high entropy effect, the lattice distortion effect, the delayed diffusion effect, and the «cocktail» effect. Obtaining nanosized high-entropy materials based on high-entropy alloys is a new promising direction that allows one to significantly expand their areas of application related to energy (catalysis, energy storage, etc.), nanoelectronics, etc. The article analyzes some methods for the synthesis of nanosized high-entropy alloys and materials based on them. basis, developed as catalysts. The improved performance over conventional catalysts is explained in terms of the effects and features specific to multicomponent systems.

Fe‐based amorphous and nanocrystalline alloys are widely used in transformers, electronic information, and aerospace applications due to their high saturation flux density (Bs), high permeability, low iron loss, and low coercivity (Hc). This article briefly introduces soft magnetic materials, gives an overview of the classification, preparation methods, soft magnetic properties, and applications of Fe‐based amorphous and nanocrystalline alloys, and reviews the effects of elements such as Fe, Co, Ni, Si, B, P, and Nb in the alloys on the properties of Fe‐based amorphous and nanocrystalline alloys such as amorphous forming ability, Bs and Hc. The challenges and development directions of Fe‐based amorphous and nanocrystalline alloys in research are pointed out. [ABSTRACT FROM AUTHOR]

With unique mechanical and functional properties, amorphous, nanocrystalline and matrix duplex microstructure membrane alloys based on group V elements actively contribute to the development of hydrogen energy. There are still not completely resolved problems for these new alloys - their low thermal stability, insufficient mechanical strength (plasticity, hardness), and intermetallic and hydride embrittlement. For effective use, alloys with a triple composition are being developed – which, in addition to the elements of group V, also include nickel and titanium as alloying metals. Not only amorphous and nanocrystalline alloys are obtained that are applicable in electronics and power engineering, as well as membrane alloys with a duplex matrix structure that combines amorphous, nano- and quasicrystalline dendritic-hardening phases strengthening the amorphous matrix. In specialized membrane ternary alloys, NiTi and NiTi2 compounds are formed, which stabilize and protect nano- and crystalline membranes from brittle destruction. It has been found that the intense formation of hydrides in these alternative membrane alloys is as undesirable as for palladium-based compounds. The alloys under consideration actually make it possible to obtain high-purity gaseous hydrogen using new compositions instead of expensive membranes based on Pd-Au/Ag/Cu alloys.

An analysis was carried out of influence of , Ti Mo and W on the nature of the amorphous nano- and crystalline structures on the strength and kinetic characteristics – diffusion D and permeability Φ of hydrogen in membrane alloys based on binary Nb - Ni and V - Ni . Doping with Nb - V alloys by titanium, molybdenum and tungsten leads to the gradual replacement of niobium and vanadium, and promotes the formation of several minor phases while acting as barriers for hydrogen diffusion, but contributing hydride reduction processes. A close dependence of the hydrogen kinetics was revealed not only on thermodynamic parameters – temperature and pressure, but also on the presence of free volume in the formed amorphous, nanocrystalline and crystalline alloys. So, the processes of selectivity, the dynamics of hydrogen – its flux J determined by the product of diffusion D and permeability Φ, J = D × Φ depend on the basic composition and the choice of alloying elements (Ti, Mo and W), as well as the formed structures – amorphous, nanocrystalline and duplex, represented by multiphase crystalline microstructures. It was found that a carefully selected composition determines the productivity of the selective process and promotes the release of high-purity hydrogen with its subsequent applications for green energy.

The alloys intended for membrane technologies for producing high-purity hydrogen and the methods of their synthesis are analyzed. Both traditional Pd-based alloys and the alloys based on cheaper Group V and VIII metals are considered using binary Nb–Ni, V–Ni, and Ta–Nb alloys with Ti, Zr, Mo, Hf and W as an example. The kinetic and strength characteristics, thermal stability, wear resistance, and stable functionality of membrane amorphous and nanocrystalline alloys with alternative compositions based on Group V elements are considered. The problems of intermetallic and hydrogen embrittlement during long-term hydrogen selection processes are considered. A solution to these problems is proposed by designing new alloys based on Group V and VIII metals alloyed with elements Ti, Mo, Hf, and W, by limiting the temperature range from 473 to 673 K, and by limiting the maximum permissible hydrogen concentrations H/M to at most 0.22. Membrane alloys of Nb(V, Ta)–Ti–Ni solid solutions with a duplex matrix structure, namely, eutectic phases and primary phases {bcc (Nb, Ti) + TiNi} + {Nb(V, Ta), Ti}, respectively, and the NiTi and NiTi2 compounds stabilizing and protecting the matrix structure against brittle destruction are also analyzed. The proposed alternative alloys make it possible to produce high-purity gaseous hydrogen using new compositions instead of expensive membranes based on Pd–Au/Ag/Cu alloys. [ABSTRACT FROM AUTHOR]

The developed membrane and battery compositions of alloys for hydrogen energy meet the requirements of producing high-purity hydrogen (>99.999%). However, their low thermal stability and insufficient mechanical strength (plasticity, hardness) remain a challenging problem. In this work, we focus on studying the processes of formation of various types of dispersed phases in matrices during melt cooling, since they determine the properties of membranes, including undesirable intermetallic and hydride embrittlement. The elimination of problems is achieved by the formation of duplex and ternary matrix structures in membranes, in which amorphous, nano-, and quasicrystalline dispersed phases can coexist with each other. Various membrane alloy compositions from Group V elements and transition metals with Ti and Ta alloying additives (Cu, Ni, Fe, V, Nb, Ta + Zr, Ti, W, Mo) are fabricated and studied. Some of them have shown excellent thermal stability, plasticity, and diffusion hydrogen permeability during membrane operation. [ABSTRACT FROM AUTHOR]

Highlights • High and room temperature structural evolution is scanned. • Electrical, mechanical and magnetic properties are measured simultaneously. • Only one sample test is employed for the whole structural evolution study. • Evolution curves present a great level of detail. • A great amount of useful data for the design are obtained with a single experiment. Abstract The structure evolution of some soft magnetic metastables alloys are scanned and studied through some room temperature properties changes employing only one sample submitted to successive heat treatments. These are monitored by changes occurring in room temperature magnetic properties (data obtained from hysteresis loop at 50 Hz and relative permeability at 10 kHz), room and high temperature electrical resistance and dilatometric measurements, all taken simultaneously. The method is applied to study and compare the structural evolution steps towards the most desirable soft magnetic properties of three different soft magnetic alloys of our production: an amorphous alloy of composition Fe 81 B 14 Si 5 , and two nanocrystalline, a Finemet™ (Fe 73.5 Si 16.5 B 6 Cu 1 Nb 3) and a Nanomet™ (Fe 81 Si 6 P 4 Cu 1 B 8) – type alloys. The technique reproduces the results obtained by traditional methods, and has the advantage of using fewer measuring instruments, sample tests, less time and human resources. In addition, all the experimental data present a high level of detail. With the results obtained, a large quantity of magnetic, electrical and dilatometric data is available to discern the possible applications of these three materials. [ABSTRACT FROM AUTHOR]

Amorphous Fe 75 Nb 10 B 15 and (Fe 70 Co 30 ) 75 Nb 10 B 15 alloys were prepared by mechanical alloying from the elemental constituents and hot compacted at different temperatures within the supercooled liquid region. After compaction, the microstructure studied by X-ray diffraction shows an increase in the crystalline fraction for both compositions. Magnetic properties and magnetic entropy change of compacted samples of the Co-free alloy were enhanced with respect to the powder sample, meanwhile, a deterioration in these properties was observed for the Co containing alloy after compaction. Both changes could be ascribed to an enrichment in boron in the amorphous phase. [ABSTRACT FROM AUTHOR]

Results concerning the magnetic, magnetostrictive, structural, morphological, and topological properties of amorphous and nanocrystalline Fe Cu Nb Si B thin films deposited using the high power impulse magnetron sputtering (HiPIMS) technique are reported. In as-deposited state, the samples are amorphous, the nanocrystalline state being achieved for samples isothermally annealed at adequate temperatures, in an electric furnace. For the optimum annealing temperature (475 C), a decrease by about 70 % for the coercive magnetic field (50 A/m) and up to 1 order of magnitude for the saturation magnetostriction (~1×10), compared to the as-deposited state, was obtained. The X-ray diffractometry (XRD) and scanning electron microscopy (SEM) results for samples thermally treated at 475 C revealed a 53.6 % crystalline volume fraction of α-Fe(Si) nanograins with an average size of about 15 nm and a Si content of 10.78 %, uniformly dispersed in a residual amorphous matrix. Using the saturation magnetostriction values determined using the cantilever deflection method and the crystalline volume fraction of α-Fe(Si) nanograins, the contribution of crystalline phase to the saturation magnetostriction was also determined. [ABSTRACT FROM AUTHOR]

Abstract: The milling time evolution of magnetic anisotropy of ball milled powders can be described considering two regimes. First, for short milling times, the main factor affecting the magnetic behavior of the alloy is the accumulation of internal stresses. Second, for long milling times, magnetic anisotropy can be explained using three contributions: long-range magnetoelastic, averaged short-range magnetoelastic and averaged magnetocrystalline anisotropies. [ABSTRACT FROM AUTHOR]

Abstract: In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni–W alloy coatings. The size of the carbide particles ranges between 100 and 500nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25ml/min, liquid) and argon (0.5L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700–850°C. The carbide–metal interface is clean and the composite coatings are compact. Hardness values up to about 1100KHN are achieved. Hardness increases with tungsten content and carburizing temperature. [Copyright &y& Elsevier]

• The introduction of nitrogen can effectively refine the grain size of FeCoHfN films. • Amorphization and the enrichment of HfN improve the high-frequency magnetic properties of the films. • Appropriate nitrogen pressure plays a key role in forming favorable microstructure and phase composition. • The transition of nanocrystalline-amorphous structure can be realized by adjusting the N element. • The film deposited at R (N 2) = 12% exhibits a high 4π M s of 16.2 kGs, a great initial μ of 293, and a high f r of 2.97 GHz. The microstructure and electro-magnetic properties of FeCoHfN thin films deposited by reactive sputtering under an in-situ magnetic field have been studied as a function of nitrogen partial pressure (R (N 2)). As the (R (N 2)) increases, the grain size of α-FeCo phase can be effectively reduced, and the structure of the films changes from an amorphous/nanocrystalline dual-phase structure with ultrafine α-FeCo magnetic nanoparticles isolated by a nonmagnetic insulating layer to a single amorphous structure. The structural transformation and the enrichment of HfN layer improve the resistivity and static and dynamic soft magnetic properties of the films. Higher resistivity is expected to reduce eddy current losses at high frequencies. The critical (R (N 2)) when the film shows indications of excellent high-frequency magnetic properties is 8%. The deposited FeCoHfN thin films have high saturation magnetization of 14.9–16.2 kGs, great permeability of 222–322 at GHz, and high ferromagnetic resonance frequency up to 3.5 GHz, showing the promise of high-frequency applications. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic properties of a recently developed Fe-based amorphous alloy with a high saturation induction of 1.65T are reviewed. The increased saturation induction is fully utilized in transformers with reduced magnetic losses, physical sizes and audible noises, minimizing some of the drawbacks of amorphous metal-based transformers based on a currently available amorphous alloy. Impacts of this on the worldwide energy savings and reduction of greenhouse gas emissions are discussed. A recent effort in achieving a saturation induction beyond 1.65T in nanocrystalline alloys is mentioned. [Copyright &y& Elsevier]

The founding of the Institute of Precision Alloys under Bardin's leadership is discussed, along with its subsequent development. [ABSTRACT FROM AUTHOR]

Controllable and fast heating profiles provide unique capabilities to realize enhanced soft magnetic properties of amorphous and nanocrystalline materials in conventional nanocrystalline alloys, as well as alloy chemistries for which carefully controlled annealing processes play a critical role in realizing desired properties tailored within a large degree of flexibility. This review aims to identify the fundamental physical phenomena in rapid thermal processing of amorphous and nanocrystalline soft magnetic alloys and to provide a comprehensive summary on the progress made to improve their performance, with an emphasis on processing in electromagnetic fields. The review begins with general background on fundamental concepts of electromagnetic heating and aspects of heat transfer followed by a detailed description of rapid thermal processing techniques employed over the relevant frequency range. These include; Joule heating, induction heating, microwave heating, and laser-assisted surface heating. In addition, traditional methods enabling high heating rates are included and reviewed accordingly. Influences of processing parameters and the detailed mechanism of heating are discussed with an assessment of experimental observations reported in the literature and further validated by simulations. Phase transformations and crystallization processes are discussed in the context of nucleation and growth kinetics, with a demonstration of thermal processing routes and alloy design. A critical evaluation of structural and magnetic properties are provided, and the underlying role of heating rates and magnetic anisotropies are highlighted. An outlook for future development trends and a number of challenges in this field are presented. Image 1 • Microstructural engineering at the nanoscale in nanocomposite soft magnetic materials. • Fundamentals of electromagnetic heating and energy transfer at the nanoscale. • Enhancing materials performance via rapid thermal processing and alloy optimization. • Spatially selective thermal processing using techniques such as radio frequency induction heating and laser annealing. • Comprehensive summary of experimental results reported in the literature to date. [ABSTRACT FROM AUTHOR]

Heat-treated Fe42.7Co42.7Zr6.8−xNbxB6.8Cu1 (x=0,1) alloys were studied. During nanocrystallization of these alloys, the ordered α′-FeCo phase is formed. Moreover, the magnetic susceptibility of the nanocrystalline alloys slightly depends on temperature. Furthermore, the relaxation processes occurring in the amorphous matrix are the main source of the magnetic susceptibility disaccommodation in nanocrystalline alloys. [Copyright &y& Elsevier]

The self-similar model of hysteresis is verified for magnetic materials such as electrical steel, amorphous and nanocrystalline alloys. It is demonstrated that this model reproduces only major hysteresis loops, whereas in the case of minor loops – the model should be extended by an additional parameter to achieve satisfactory agreement between modelled and measured hysteresis loops. [ABSTRACT FROM AUTHOR]

Microstructure and magnetic properties of metalloid-free (Fe 100− x Co x ) 90 Zr 10 amorphous and nanocrystalline alloys were characterized. Devitrification of these amorphous alloys occurs in two overlapped transformations leading to the formation of α-Fe(Co) and Fe(Co)Zr 2 phases. Constant local Avrami exponents have been found for each individual process. Although Co-free alloy shows a larger grain size, crystalline fractions are similar for both alloys after equivalent annealing. Good soft magnetic properties at room temperature have been observed for amorphous and nanocrystalline alloy with x = 30, which exhibits an amorphous Curie temperature of 735 K. The x = 0 amorphous alloy is paramagnetic at room temperature and nanocrystalline samples exhibit a transition to superparamagnetic behavior. [ABSTRACT FROM AUTHOR]