Introduction. High-entropy alloys (HEAs) belong to a new and promising class of materials that are attracting the attention of both scientists and engineers from all over the world. Among all alloys of the AlxCoCrFeNi system, HEAs with x ≤ 0.3 attract special attention. Materials with this composition are characterized by the presence of only one phase with a face-centered cubic lattice (FCC). Such alloys have high ductility, excellent corrosion resistance and phase stability at high temperatures. The purpose of this work is to compare several methods of profile analysis on the example of plastically deformed ingots of a high-entropy Al0.3CoCrFeNi alloy. The methods of investigation. Using several methods of profile analysis of X-ray diffraction patterns, the structures of the cold-worked high-entropy alloy Al0.3CoCrFeNi are studied. In addition to the classical Williamson-Hall method, the analysis was carried out using a modified one, as well as a method that takes into account the anisotropy of the elastic properties of the crystal lattice. Research material. Ingots of the high-entropy Al0.3CoCrFeNi alloy deformed by cold rolling with a maximum reduction ratio of 80% were used as the object of the study. Samples were cut from the obtained blanks, which were studied by the method of synchrotron radiation diffraction according to the “transmission” scheme along two (longitudinal (RD) and transverse (TD)) directions of rolled products. Results and discussion. It is shown that the use of the classical Williamson-Hall method leads to a significant error in the approximation of experimental results. The modified Williamson-Hall method has the smallest approximation error and can be recommended for studying the Al0.3CoCrFeNi alloy. An analysis of deformed samples using this method made it possible to reveal several features of the formation of defects in the crystalline structure, which are in good agreement with the classical concepts of the mechanisms of plastic deformation. First, an increase in the degree of deformation of the high-entropy Al0.3CoCrFeNi alloy leads to an almost uniform increase in the number of twins and stacking faults. Secondly, with an increase in the degree of reduction, there is a decrease in the fraction of edge dislocations and an increase in the fraction of screw dislocations in the material. The results obtained correlate well with the results of microhardness measurements.

The paper considers the features of structural transformations during annealing of the high-entropy alloy Al_0.3CoCrFeNi. 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.

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_0.3CoCrFeNi 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 HV_0.1 (for the deformed material), the microhardness during heat treatment increases up to 587 ± 10 HV_0.1.

The study analyzes the effect of laser power and velocity on the structural phase state and properties of complex-alloyed titanium alloy VT23 (Ti–Al–V–Mo–Cr–Fe) obtained by direct laser deposition. VT23 titanium alloy has a unique combination of strength, corrosion resistance, and biocompatibility, which makes it in demand in the aerospace and medical industries. However, traditional manufacturing methods (casting, stamping) often fail to provide the required accuracy and quality of complex parts. In this work, X-ray phase analysis and optical metallography revealed that the deposited samples consist of α- and β-phases (~20 % β-phase) with a typical “basket weave” structure. In macrostructure of the obtained samples, thermal bands and interlayer boundaries were recorded, the formation of which is associated with the peculiarities of crystallization process during direct laser deposition. The results of optical metallography showed that microstructure of the deposited material combines large columnar crystals in the overlap areas of two adjacent layers, as well as small equiaxed grains. Despite this distribution of structural components, the microhardness (~488 HV _0.2 ) remains homogeneous throughout the deposited samples in both the laser scanning and sample deposition directions. The results confirm that direct laser deposition can be used to produce VT23 titanium alloy parts with a controlled microstructure. Optimization of the process parameters of direct laser deposition minimizes the probability of defect formation and provides stable mechanical properties, which opens prospects for application of the technology in the production of critical parts.