Investigation of the structure and properties of AlCrCuFeNiVx high-entropy alloys

Co-free AlCrCuFeNiVx (x = 0.2, 0.6, 1.0) high-entropy alloys were designed for the potential use as a friction material. The influence of the V content on the microstructure, component segregation, phases distribution, micro-hardness, and wear resistance of AlCrCuFeNiVx alloys was investigated in detail. The microstructure of the alloys with V contents lower than x = 0.6 was mainly comprised of simple body-centered cubic (Fe-Cr-V type BCC phase) and face-centered cubic (Ni-Cu-Al type FCC phase) duplex structures and a small amount of ordered intermetallic phases. When the V content in the alloys was x = 1.0, two kinds of BCC structures were dominant in the alloys, namely the AlFeV2 type metastable phase and the Fe-Cr-V type phase. The increase in the V content in the alloys altered the distribution of Cu, Ni, and Al, thereby promoting the segregation of Cu and weakening the segregation of Ni and Al. Heat treatment at 1000 degrees C for 2 h promoted the precipitation of the M3Al intermetallic phase and the decomposition of the metastable phases, increasing the component segregation. The microhardness of the alloys first increased with increasing V content and then decreased slightly after the V content reached x = 1.0. After the heat treatment, the microhardness was lower for the AlCrCuFeNiV0.2 and AlCrCuFeNiV0.6 alloys and higher for the AlCrCuFeNiV1.0 alloy due to precipitation strengthening and grain boundary strengthening. The delamination wear mechanism changed from adhesion to abrasive wear with the increase in the V content.