The article considers a brief review of the foreign publications on the study of the structure, phase composition and properties of five-component high-entropy alloys (HEAs) in different structural states in a wide temperature range over the past two decades. HEAs attract the attention of scientists with their unique and unusual properties. The difficulties of comparative analysis and generalization of data are noted due to different methods of obtaining HEAs, modes of mechanical tests for uniaxial compression and tension, sizes and shapes of the samples, types of thermal treatments, and phase composition (bcc and fcc crystal lattices). It is noted that the HEA with a bcc lattice has mainly high strength and low plasticity, and the HEA with a fcc lattice has low strength and increased plasticity. A significant increase in the properties of the FeMnCoCrNi HEA with a fcc lattice can be achieved by alloying with boron and optimizing the parameters of thermal mechanical treatment at alloying with carbon in the amount of 1 % (at.). The deformation curves analyzed in the temperature range –196 ÷ 800 °C indicate an increase in the yield strength with a decrease in the grain size from 150 to 5 microns. As the temperature decreases, the yield strength and elongation increase. The effect of deformation rate on the mechanical properties is an increase in the ultimate strength and yield strength, which is most noticeable at high rates of 10^–2 ÷ 10³ s^–1. The features of HEAs deformation behavior in the mono- and poly-crystalline states are noted. The complex of high operational properties of HEAs makes it possible to use them in various industries. There are good prospects of using energy treatment to modify the surface layers and further improve HEAs properties.

High-current pulsed electron-beam (HCPEB) surface modification of Al-Co-Cr-Fe-Ni high-entropy alloy (wt. %) Al—15.64; Co—7.78; Cr—8.87; Fe—22.31; Ni—44.57, fabricated via wire-arc additive manufacturing was studied. The initial condition of the sample is characterized by a highly inhomogeneous distribution of the chemical elements that form the alloy. The alloy samples were irradiated with the different electron beam energy densities of 10, 20 and 30 J/cm². The surface structure was then analyzed in relation to an energy deposition mode. The study has established that HCPEB induces a high-speed crystallization structure with cells varying in size from 100 to 200 nm. There are nano-dimensional (15–30 nm) second-phase inclusions enriched with atoms of Cr and Fe along the grain boundaries. The most liquating elements are Cr and Al. Electron beam surface modification of the high-entropy alloy induces its homogenization. The study has highlighted that the mode of 20 J/cm², 50 µs, 3 pulses, 0.3 s⁻¹ results in the formation of a surface layer with the most homogenously distributed chemical elements.

Fabrication of high-entropy alloys (HEAs) is a crucial area of interest for materials scientists since these metallic materials may have many practical uses. Wire arc additive manufacturing (WAAM), unlike other additive technologies, has tangible benefits for making large-sized components, but manufacturing the wire from HEAs is still very limited. Recent studies suggested tackling this problem using a combined cable composed of wires consisting of pure elements as feeding material. However, not all compositions of HEAs can be obtained by the pure elements’ wires because the number of them is limited. This study aims to examine phase composition, chemical elements distribution, microstructure, and mechanical properties of a Co-Cr-Fe-Mn-Ni HEA, which was not previously obtained by the WAAM. The cable-type wire used in this study is composed of two wires which consist of Cr, Fe, Mn, and Ni, and one pure Co wire. The phase composition, chemical elements distribution, microstructure, and mechanical properties were investigated. The prepared high-entropy alloy has non-equiatomic chemical composition with a single-phase FCC crystal structure with homogeneously distributed elements inside the grains. The microstructure examinations showed dendrite structure which is typical for WAAM processes. The compressive yield strength of the alloy is ~279 MPa, the ultimate compressive strength is ~1689 MPa, the elongation is 63%, and the microhardness is ~150 HV, which was found to be similar to the previously fabricated Co-Cr-Fe-Mn-Ni alloys by other methods. Fracture analysis confirmed the ductile behavior of deformation by the presence of dimples.

Gas metal arc welding based on wire arc additive manufacturing was adopted to fabricate a non-equiatomic Al_2.1Co_0.3Cr_0.5FeNi_2.1 thick-walled component. The combined cable wire composed of three filaments with different elemental compositions was used as the feeding material. The microstructure and mechanical properties of the as-deposited component were investigated. The deposited sample consisted of dendrite grains ranging in size from 5 to 15 µm and interdendritic regions. The compressive yield strength and ultimate compressive strength of the obtained material are 550 and 1899 MPa. The microhardness test revealed an average value of 463 HV. The nanohardness and the elastic modulus of the sample are 10.4 and 304 GPa, respectively. Energy-dispersive spectroscopy showed that the elemental distribution in the top, middle, and bottom areas of the sample is uniform. X-ray diffraction analysis revealed two main phases of Al-Ni-Co-rich B2 and Fe-Cr-rich A2 in the material.

The article considers a brief review of the last years of Russian and foreign research on the possibilities of improving mechanical properties of the Cantor quinary high­entropy alloy (HEA) with different phase composition in wide temperature range. The alloy, one of the frst created equimolar HEAs with FCC structure, needs mechanical properties improvement in accordance with possible felds of application in spite of its high impact toughness and increased creep resistance. It has been noted that bimodal distribution of the grains by sizes under severe plastic torsional strain at high pressure of 7.8 GPa of cast alloy and subsequent short­time annealing at 873 and 973 K can change strength and plastic properties. Nanodimensional scale of the grains surrounded by amorphous envelope has been obtained for HEA produced by the method of magnetron sputtering and subsequent annealing at 573 K. In such a two­phase alloy nanohardness amounted to 9.44 GPa and elasticity modulus – to 183 GPa. Using plasticity effect induced by phase transformation in (CrMnFeCoNi)50Fe50 alloy obtained by the method of laser additive technology the ultimate strength of 415 – 470 MPa has been reached at high level of plasticity up to 77 %. It has been ensured by FCC → BCC diffusionless transformation. It is shown that difference in mechanisms of plastic strain of cast alloy at 77 K and 293 K (dislocation glide and twinning) determines a combination of increased “strength­plasticity” properties. Samples for generation of twins prestrained at 77 K exhibit increased strength and plasticity under subsequent loading at 293 K in comparison with the unstrained ones. For HEA obtained by laser additive technology this way of increasing properties is also true. The way of improving mechanical properties at the expense of electron beam processing is noted. The attention is paid to the necessity of taking into account the role of entropy, crystal lattice distortions, short­range order, weak diffusion and “cocktail” effect in the analysis of mechanical properties.