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Using the technology of wire-arc additive manufacturing (WAAM), a high-entropy alloy (HEA) of the nonequiatomic composition Al, Cr, Fe, Co, and Ni is manufactured. Using the methods of modern physical materials science, the elemental and phase composition, defective substructure, and mechanical and tribological properties of the HEA surface layer formed as a result of complex modification combining deposition of a film (B + Cr) and irradiation with a pulsed electron beam in an argon medium are analyzed. In the initial state, the alloy has a simple cubic lattice with a lattice parameter of 0.28795 nm; the average grain size of the HEA is 12.3 µm. Chemical elements (at %) 33.4 Al; 8.3 Cr; 17.1 Fe; 5.4 Co; and 35.7 Ni, which form the HEA, are distributed quasi-periodically. The irradiation regime is revealed (electron beam energy density ES = 20 J/cm2, pulse duration 200 µs, number of pulses 3, and frequency 0.3 s–1 more than 5 times), allowing one to increase microhardness (almost by 2 times) and wear resistance (by more than 5 times) and reduce the coefficient of friction by 1.3 times. Regardless of the value of Es, the HEA is a single-phase material and has a simple cubic crystal lattice. High-speed crystallization of the surface layer leads to the formation of a subgrain structure (150–200) nm. It is shown that an increase in the strength and tribological properties of the HEA is due to a significant (4.5 times) decrease in the average grain size, the formation of particles of chromium and aluminum oxyborides, and the incorporation of boron atoms into the crystal lattice of the HEA. [ABSTRACT FROM AUTHOR]

The paper presents results of transmission electron microscopy of the plasma coating/substrate interface. Its elemental and phase compositions and defect substructure are investigated. The high-speed steel R18-Yu coating is deposited in argon medium onto the type 30HGSA steel substrate high-tempered for several times. It is shown that both the coating and substrate are mutually alloyed. Primarily the substrate demonstrates a multi-phase, multi-element sub-nanoclystalline structure with the lamellar morphology. It is shown that multiple high-temperature tempering leads to the formation of carbide nanoparticles both in the volume and at the boundaries of the martensite lath structure. [ABSTRACT FROM AUTHOR]

The development of alloys called high-entropy alloys, which consist of several (usually five or more) basic elements, in contrast to conventional alloys with one and rarely two basic elements, indicates the emergence of a new class of metallic materials with a unique combination of mechanical, physical, tribological, and other properties. The aim of this work is to analyze the results obtained in the study of the elemental and phase composition, and defect substructure of multilayer multielement nanostructured metal films (so-called high-entropy alloys of nonstoichiometric composition) by X-ray diffraction analysis and transmission diffraction electron microscopy. Films of high-entropy alloys are formed by depositing a metal plasma onto a substrate, which is formed as a result of the vacuum arc plasma-assisted simultaneous independent evaporation of cathodes of the following groups of metals: Nb, Mo, Cr, Ti, Al (sample 1) and Ti, Al, Cu, Zr, and Nb (sample 2). The elemental composition of the films is revealed. It is found that the obtained films are multilayer and have a nanocrystalline structure. Sample 1 is a single-phase material based on a MoNbCrTiAl solid solution with a body-centered cubic (bcc) crystal lattice with a parameter of 0.3166 nm. Sample 2 is an X-ray amorphous material. It is found that the microhardness of films 1 deposited on VK8 hard alloy turns out to be higher than that of films 2. [ABSTRACT FROM AUTHOR]

Solid-phase sintering was used to make ceramic from a mixture of ZnO, SnO2, and TiO2 nanopowders used as precipitation-strengthening and arc-quenching components in silver-based electrocontact materials. The phase formation and microstructure of the resulting material were studied by electron microscopy, energy-dispersive microanalysis, and x-ray phase analysis. It was found that a dispersed structure of size 0.5 – 1.0 μm forms from the Zn2TiO4 and ZnO phases at sintering temperature 1123 K, and the samples have quite high porosity. Solid-phase reactions in the ZnO/TiO2 system at Tsint = 1123 K effect the formation of two-phase ZnO/Zn2TiO4 ceramic with zinc and tin oxide phases in residual amounts. At sintering temperature 1443 K grain growth occurs, Zn2SnO4 becomes the predominant phase, and a certain amount of zinc and tin oxide phases remains. There is no manifestations of titanium-containing phases (presumably TiO2 and Zn2TiO4), probably because of their low content. [ABSTRACT FROM AUTHOR]

According to the technology of wire-arc additive manufacturing a nonequiatomic composition CoCrFeMnNi high-entropy alloy (HEA) was obtained. Deformation curves of samples in tension are plotted and analyzed after the HEA fabrication by the methods of wire-arc additive manufacturing (initial state) and after the electron-beam processing (EBP). The EBP results in a decrease in the HEA's strength and plastic properties. Along with a pit character of the fracture a presence of micropores and microlayerings are identified. A study of the HEA's fracture surface after the EBP except for regions with a ductile fracture mechanism revealed regions with a band (lamellar) structure. The area with a band structure increases with a growth in the beam electron density from 25% at 10 J/cm2 to 65% at 30 J/cm2. A diameter of separation pits in fracture bands varies in the limits (0.1–0.2) μm, which is considerably less than those of the remaining part of the HEA sample. An average size of crystallization cells formed in the EBP depends on the energy density of electron beam and increases from 310 nm at 15 J/cm2 to 800 nm at 30 J/cm2. A non-monotonous change in the scalar dislocation density, reaching a maximum value of ∼5.5 · 1010 cm-2 at a distance of 25 μm from the irradiation surface is revealed. It is suggested that defects being formed in surface layers in the EBP may be one of the reasons for decreasing the values of HEA strength and plasticity.

Pulsed plasma flow treatment of materials has been insufficiently studied, which makes it impossible to estimate the main parameters of the modified layer. Thus, the treatment mode is selected experimentally for each individual material to obtain the optimal hardening layer thickness and microhardness. In this scientific study, structural steels 45, 20Kh and 40KhN2MA were irradiated for different durations and number of pulses, followed by investigation of the elemental and phase composition, microhardness and thickness of the hardening layer. [ABSTRACT FROM AUTHOR]

Silumin (an alloy of aluminum with silicon) is a cheap industrial alloy with good corrosion resistance, high specific mechanical properties and good casting properties. As a result it has found wide applications in modern industry (aircraft and mechanical engineering, instrument making, shipbuilding, etc.). The aim of this work is to analyze the regularities of transformation of the structure and phase composition of the surface layer of a hypereutectic silumin ( Al - 22 wt % Si ), subjected to irradiation with an intense pulsed electron beam. It was found that irradiation of silumin with a pulsed electron beam ( 18 keV, 25 J / cm^2, 200 μs, 3 pulses, 0,3 s^(-1)) leads to melting of the surface layer up to 60 μm thick, the high-speed crystallization of which is accompanied by the formation of a submicro-nanocrystalline multiphase structure. It is shown that aluminum (a solid solution based on fcc crystal lattice) forms cells of high-speed crystallization; nanoscale particles of the second phases are located at the cell boundaries. Analysis of three-component state diagrams of the Al - Si - Fe - Cu system (the main elements of the studied silumin) demonstrated the possibility of forming a large number of two- and three-element compounds in the alloy under equilibrium conditions. It has been shown by diffraction electron microscopy that, along with three-element phases, phases based on four and, possibly, more elements are formed in silumin.

Stable ethylene glycol (EG) and propylene glycol (PG) electrolytes containing СuCl2 · 2H2O, SnCl4 · 5H2O and Trilon B have been developed, which provide electrodeposition of Cu – Sn alloy with tin content varying from 34 to 52 at. % in case of EG and from 51 to 91 at. % in case of PG electrolytes. It is found that the coatings contain phases of Cu6Sn5 и Cu10Sn3 intermetallic compounds, and metallic tin is also present in case of its highest content in the alloy. It is revealed that tin content can be simply varied by the change of current density or concentrations of tin and copper compounds in glycols. The effect of electrolyte composition, deposition conditions, a nature of a substrate on the coatings deposition rate (in the limits of 0.9‒2.9 μm ∙ h‒1), total metal current efficiency (from 40 to 95 %), the ratio of metals in the alloy (from 34 to 91 at. %), its phase composition and microstructure is determined. The conditions for the deposition of Cu – Sn alloy close to the eutectic composition have been found.

This paper presents results of the research aimed at the creation of the ilmenite-fluorite welding flux using mineral raw materials of the Far Eastern region of Russia. To analyze possible physical and chemical processes in the slag system, thermodynamic calculations were carried out. The experimental research resulted in mathematical dependences that make it possible to select flux components that would ensure the desired properties of the hardfacing surfaces formed. Experimental overlay welding sessions were performed to determine the welding-technological characteristics and properties of the weld deposit. It was shown that the flux consisting of 50% of the mineral components extracted in the Far Eastern region and 50% of the standard flux АN22 is basic (basicity В = 1.46) and has low oxygenation capacity (А = 0.22). This facilitates reduction processes in the slag bath and, as a consequence, allows obtaining high quality weld deposits. The required mechanical and performance properties of the coatings formed are maintained owing to the reduction of alloying elements and possible formation of carbides (CrFe)7C3 or (CrFe)23C6, alloyed cementite (CrFe)7C3, and other substances. As an example, the weld deposit produced by overlay welding using the AN22PK-DMS flux is characterized by the highest content of chromium (12–15%) and the highest content of manganese (6%). [ABSTRACT FROM AUTHOR]

Composition and working conditions of stable fluoride-chloride electrolyte with the diminished nickel chloride content have been found based on the experimental data on the effect of pH, current density, the nature and concentration of components on composition, microstructure and properties of the electrodeposited nickel – tin alloy. In the absence of modifying additives this electrolyte provides plating of uniform, dense and unstressed Ni – Sn coatings which consist of dominating Ni3Sn4 phase and contain 35 at. % of nickel. These coatings have the raised corrosion stability and solderability for a long period of aging. The principal effect of the electrolyteʼs pH (optimal 4.0) on the stability of the solution and coatings quality has been shown. It is revealed that nickel and tin simultaneous reduction proceeds with the depolarizationN effect stipulated by the alloy formation.

This article presents a comprehensive study of the Zr B N coating characterized by high transmittance. The coating was deposited by magnetron sputtering of a ZrB 2 target in nitrogen atmosphere. The coating structure was studied by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and glow-discharge optical emission spectroscopy. The mechanical properties were assessed by nanoindentation. The transmittance and reflectivity, as well as the refractive index, were measured by spectrophotometry. Special attention was paid to in situ transmission electron microscopy studies of thermal stability of the coatings at different heating temperatures and exposure times. Due to the high volume fraction of the BN phase and low defect density, the coating was characterized by transmittance of 70–90 % in the wavelength range of 600–2500 nm. The films exhibit high elastoplastic characteristics (H/E = 0.076 and H3/E2 = 0.057 GPa) and thermal stability at temperatures up to 800 °C. • Optically transparent Zr B N coatings were obtained by DC magnetron sputtering. • High transmittance of 70–90 % was associated with a high volume fraction of the BN phase. • Coatings exhibited a hardness of 10 GPa and an elastic recovery of 67 %. • In situ TEM studies revealed a thermal stability of the coatings up to 800 °C. [ABSTRACT FROM AUTHOR]