When choosing compositions of high-entropy alloys, one of the parameters taken into account is thermal stability. The paper considers the structural transformations of the deformed Al0.3CoCrFeNi high-entropy alloy occurring during its annealing. The material was obtained by argon-arc melting with a mixture of pure single-element components. In order to homogenize the structure, the resulting ingot was subjected to thermomecha­nical processing according to a scheme combining cold rolling with a compression ratio of 50 % and low-temperature annealing (400 °C for 100 h). In the future, the homogenized billet was rolled in a cold state with a compression ratio of 80 %. The structure of the materials was studied directly during heating (in-situ mode) using the method of synchrotron X-ray diffraction. The heating rate of the samples was 20 °C/min, the maximum heating temperature was 1000 °C. The parameters of the alloy dislocation structure (density of screw dislocations, spatial distribution of dislocations) during heating were determined using the modified Williamson–Hall and Warren–Averbach methods. According to the data obtained, the temperature of beginning of formation of a high-entropy phase with a primitive cubic lattice is 560 °C. In the process of heating the material up to this temperature, an increase in density of screw dislocations and formation of a disordered dislocation structure are observed. The nature of change in dislocation density correlates well with the increase in the alloy microhardness. At an initial value of 406 ± 13 HV0.1 (for the deformed material), the microhardness during heat treatment increases up to 587 ± 10 HV0.1 .

When choosing compositions of high-entropy alloys, one of the parameters taken into account is thermal stability. The paper considers the structural transformations of the deformed Al 0.3 CoCrFeNi high-entropy alloy occurring during its annealing. The material was obtained by argon-arc melting with a mixture of pure single-element components. In order to homogenize the structure, the resulting ingot was subjected to thermomecha­nical processing according to a scheme combining cold rolling with a compression ratio of 50 % and low-temperature annealing (400 °C for 100 h). In the future, the homogenized billet was rolled in a cold state with a compression ratio of 80 %. The structure of the materials was studied directly during heating ( in-situ mode) using the method of synchrotron X -ray diffraction. The heating rate of the samples was 20 °C/min, the maximum heating temperature was 1000 °C. The parameters of the alloy dislocation structure (density of screw dislocations, spatial distribution of dislocations) during heating were determined using the modified Williamson–Hall and Warren–Averbach methods. According to the data obtained, the temperature of beginning of formation of a high-entropy phase with a primitive cubic lattice is 560 °C. In the process of heating the material up to this temperature, an increase in density of screw dislocations and formation of a disordered dislocation structure are observed. The nature of change in dislocation density correlates well with the increase in the alloy microhardness. At an initial value of 406 ± 13 HV 0.1 (for the deformed material), the microhardness during heat treatment increases up to 587 ± 10 HV 0.1 .

The paper considers the features of structural transformations during annealing of the high-entropy alloy Al0.3CoCrFeNi. The ingots obtained by argon arc melting were subjected to cold rolling with a compression ratio of 50 %. The produced worpieces were annealed in the furnace for 4 hours at temperatures of 200, 400, 600, 800 and 1000 °C. The samples obtained by the described technique were examined using the methods of synchrotron X-ray diffraction in the lumen mode and diffraction of backscattered electrons. The research data indicate that up to a temperature of 600 °C, the structure of the alloys is represented by a single phase with a face-centered cubic lattice. When annealing alloys at temperatures of 800 and 1000 °C, the phase composition is characterized by the presence of two phases: a disordered phase with a face-centered cubic lattice and an ordered phase with a primitive cubic lattice. At temperatures above 800 °C, the burning of alloys is accompanied by development of recrystallization processes. It was found that after annealing at 800 °C, the relative proportion of micro-volumes characterized by inter-angular misorientation of more than 10° was 20 %, and after annealing at 1000 °C – 65 %. Microhardness of the studied samples increases with an increase in temperature up to 600 °C and decreases with a further increase in temperature. Analysis of the width of diffraction maxima using the methods of profile analysis of diffractograms indicates an increase in distortions of the crystal lattice of the ordered phase. This behavior may be associated with the release of nanoscale inclusions in the matrix of the main phase.

The structure of layers based on self-fluxing nickel alloy, niobium, and amorphous boron deposited by non-vacuum electron beam cladding and then subjected to a heat treatment (with fusion of the surface layer) is investigated. The cladding is conducted by two methods, i.e., (1 ) heating in a furnace chamber to 1000°C, quenching and low tempering and (2 ) heating by a high-energy electron beam (the beam current is varied from 2 to 35 mA). It is shown that the heat treatment produces substantial structural changes and redistribution of the chemical elements. The microhardness of the clad layer decreases somewhat at the surface after the fusion in the furnace chamber and remains unchanged after the electron beam treatment.

Исследована структура наплавленных слоев на основе самофлюсующегося никелевого сплава, ниобия и аморфного бора, нанесенных с использованием технологии вневакуумной электронно-лучевой наплавки и затем подвергнутых термической обработке (с оплавлением поверхностного слоя) двумя способами: 1 - нагрев в печной камере до 1000 °C, закалка и последующий низкий отпуск; 2 - нагрев высокоэнергетическим электронным лучом (ток пучка варьировали от 25 до 35 мА). Установлено, что в процессе термической обработки в наплавленном слое происходят существенные структурные изменения и перераспределение химических элементов. Микротвердость наплавленного слоя после оплавления в печной камере несколько снижается у поверхности, а после обработки электронным лучом не изменяется.

Introduction. The formation of protective layers on working surfaces of machine parts comprised of chromium-nickel austenitic steels is an effective way to increase its reliability and durability. Ni-base self-fluxing alloys are widely used in order to create wear resistant coatings. The possibility of increasing the set of properties of Ni-Cr-Si-B alloys by adding reinforcing compounds to its matrix or by synthesizing reinforcing phases directly in the process of forming a protective layer is a significant interest of domestic and foreign scientists. The literature does not provide the information on the formation of protective layers on the surface of austenitic steels using cladding by relativistic electron beams of a Ni-Cr-Si-B alloy in combination with hardening additives. Aim of the current work is to increase the tribotechnical properties of the surface layers of steel workpieces via air-revealed electron beam cladding of a Ni-Cr-Si-B alloy in combination with amorphous boron taken in different weight ratios. The proportion of amorphous boron in the powder mixture is 5, 10, and 15 wt. % respectively. The structural features of the cladded layers are investigated by using the following research methods: optical metallography (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron microprobe analysis (EMPA). The properties of the surface hardened materials are determined by microhardness investigations and wear resistance during friction against fixed abrasive particles and under conditions of hydroabrasive treatment. Results and discussion. The material produced during cladding of a Ni-Cr-Si-B alloy in combination with 15 wt. % boron is characterized by the maximum microhardness (1000 HV) and wear resistance under various wear conditions. The main structural factor providing an effective increase in the operational characteristics is the formation Fe2B, (Cr, Fe)B borides. It is shown that during Ni-Cr-Si-B alloy +15 wt. % boron cladding precipitation compounds are characterized by phase heterogeneity. The inner part of the two-phase complex particles is CrB2 around which (Fe, Cr)2B is released.