We produced silicon-containing CrFeCoNi high-entropy alloy (HEA) deposits using the low-pressure plasma spraying method and assessed their structural and characteristic properties. The alloy deposits, once manufactured, underwent a heat treatment process, during which we closely examined the formation of precipitates. These HEAs were fabricated on substrates, regardless of whether they were subjected to water-cooling or not. In the case of both deposits acquired with and without water-cooling of the substrates, diffraction peaks corresponding to the face-centered cubic (FCC) phase were clearly observed when subjected to high temperature heat treatment at 1273 K. Additionally, we identified the presence of silicon-containing compounds on the deposits. As the heat-treatment temperatures increased, we observed the coarsening of the precipitates. Notably, within the crystal granules of the water-cooled as-sprayed deposits, nanoscale precipitates were generated. Among all the samples, deposits heat-treated at 973 K exhibited the highest precipitate area fraction and hardness. This suggests a correlation between the heat treatment temperature and the resulting properties of the HEA deposits, with 973 K being the point at which the highest precipitate area fraction and hardness were achieved.

A unique deformation microstructure introduced by 20% cold rolling in a Ti-25mass%Nb-25mass%Zr (TNZ) Harmonic Structure (HS) alloy has been studied in detail by crystallographic analysis. The HS consists of soft, coarse-grained regions (Core) that are three-dimensionally surrounded by an interconnected network of hard, ultrafine-grained regions (Shell). The {332}<113> deformation twins are observed in the deformation microstructure of the homogeneous grained TNZ alloy compacts with a sinter holding time of 1.8 ks. In contrast, in the deformation microstructure of the TNZ alloy HS compacts with a sintering holding time of 1.8 ks, deformation bands by slip deformation are observed in Core region. In the deformation microstructure of the TNZ alloy HS compact with a sintering holding time of 0 s, a composite deformation microstructure consisting of two types of deformation bands, {332}<113> deformation twins and <110> axial rotation slip bands, is observed in Core region. It is noteworthy that the same HS material has different deformation structures depending on the sintering time. The reason for the formation of different deformation structures is the effect of the diffusion of Fe elements doped by mechanical milling.

An attempt was to synthesis CrMnFeCoNi high entropy alloys (HEA) by mechanical alloying (MA) process, and to fabricate composites Al with CrMnFeCoNi powder by the MA-spark plasma sintering (SPS) process. HEA is typically prepared with equal atomic weight. However, there is no significant difference in the atomic amounts of Cr, Mn, Fe, Co and Ni. Therefore, CrMnFeCoNi HEA were prepared under two conditions of equal atomic weight (at%) and equal mass (mass%). The hardness and constituent phases of those two types were evaluated by micro-Vickers hardness test and X-ray diffraction, respectively. CrMnFeCoNi HEA could be obtained by MA process for 16 h for both at% and mass%. No significant differences in hardness and constitute phases were observed in obtained MAed 16 h powders for both at% and mass%. The MA process was applied to synthesize a composite powder of Al and CrMnFeCoNi HEA. The CrMnFeCoNi in Al decomposed to form compounds with Al during the sintering process. The highest hardness was achieved in the SPS material with 30 mass% CrMnFeCoNi addition, showing 438 HV, more than 250 HV higher hardness than A7075-T6.