High-entropy alloys are a unique class of alloys with high strength and hardness, good enduring quality and corrosion resistance, as well as other attractive mechanical properties for both scientific research and practical applications. Using these unique alloys together with the dynamically developing technology of laser direct energy deposition (L-DED) carries the prospects of obtaining large-sized complex-profile products with specified increased mechanical properties. The study of the influence of L-DED parameters on the formation of high-entropy alloys will expand knowledge about the influence of temperature and cooling rate on the formation of the structure, on the mechanical characteristics of high-entropy alloys and the formation of defects and use them for thermal processes involving high-entropy alloys. Preliminary modeling will predict the phase composition of alloys in conditions of high heating and cooling rates. In the work, optimal parameters were selected for obtaining high-entropy alloys based on FeCoNiCrMn by L-DED technology. It was also shown that FeCoNiCrMn alloys were divided into areas with a high content of elements (Fe, Co, Cr) and (Mn, Ni, Cu).

High-entropy alloys (HEAs) have shown promise as materials with improved mechanical properties compared to traditional materials. Achieving the desired mechanical properties depends on the alloy composition, both in terms of percentage and elements. Laser directed energy deposition technology allows for the production of products with various complex geometries and dimensions (L-DED). It has been found that HEA FeCoNiCrCu alloys can be divided into regions with high concentrations of Fe + Co + Cr and Cu elements. Dendrite growth directions of HEA FeCoNiCrCu are (111) and (200), and the average microhardness is around 240 HV. All samples have cracks vertically along the height. Fine-grained and dendrite structures were observed. Cu-element is mainly found in cracks. The HEA FeCoNiCrCu alloy was compared with another HEA FeCoCrMnNi, successfully obtained by the same L-DED technology. Comparing the two HEAs FeCoNiCrCu and FeCoCrMnNi obtained with the same deposition parameters can help determine the impact of one element on the phase composition, microstructure and mechanical properties of the high-entropy alloy. Replacing the element Mn with Cu in HEA FeCoNiCrMn led to a shift in the dendrite growth from one to two predominant directions and a decrease in the average microhardness by 20%.

The temperature dependence of the mechanical properties of the CoCrFeNi medium-entropy alloy (MEA) manufactured by laser-directed energy deposition (L-DED) and additionally annealed at 1200 °C for 24 h was studied. The microstructure of the as-deposited alloy was represented by a single-phase face-centered cubic structure with coarse columnar grains and a high density of dislocation. Annealing resulted in the development of recrystallization and a reduction in dislocation density. The CoCrFeNi alloy produced by L-DED demonstrated mechanical properties comparable with those of the fine-grained equiatomic CoCrFeMnNi alloy, produced by casting followed by thermomechanical processing. Namely, as-deposited CoCrFeNi had a yield strength (YS) and ultimate tensile strength (UTS) of YS = 370 MPa and UTS = 610 MPa at room temperature, and YS = 565 MPa and UTS = 965 MPa at cryogenic temperature, along with a ductility of ~60%. Annealing resulted in a decrease in strength to YS = 180/350 MPa at 293/77 K. A quantitative analysis of various strengthening mechanisms showed that some strength increment of the as-deposited alloy was ensured by the high dislocation density formed during L-DED.

This study investigates the microstructure and mechanical properties of a refractory Ti ₂ NbZr complex concentrated alloy fabricated for the first time by laser-based directed energy deposition (DED-LB) from a pre-alloyed powder. The optimal processing parameters were identified; specifically, a laser power of 1600 W ensured a minimum porosity of 0.031 %. Comprehensive analysis revealed the formation of a single-phase BCC structure with a heterogeneous morphology, in which large columnar grains alternated with layers of fine equiaxed grains. The average grain size decreased with increasing specimen height. Mechanical testing demonstrated a favorable combination of strength and ductility, with a yield strength of ~810 MPa, an ultimate tensile strength of ~815 MPa, and an elongation of 16 %. A theoretical assessment of the contributions of the strengthening mechanisms showed good agreement with the experimental data. Solid-solution strengthening was found to make the dominant contribution to the alloy strength. The results confirm the potential of DED-LB for manufacturing high-quality Ti ₂ NbZr components with mechanical properties superior to those of counterparts produced by conventional and additive technologies.