Microstructure and mechanical properties of twinned Al0.5CrFeNiCo0.3C0.2 high entropy alloy processed by mechanical alloying and spark plasma sintering

Most of multi-component high entropy alloys (HEAs) only consist of metallic elements. In the present paper, by introducing nonmetallic carbon element, non-equiatomic Al0.5CrFeNiCo0.3C0.2 HEA has been successfully prepared by mechanical alloying (MA) and spark plasma sintering (SPS) process. Alloying behavior, microstructure, phase evolution and mechanical properties of the alloy were investigated systematically. During the MA process, a supersaturated solid solution with both face-center cubic (FCC) and body-center cubic (BCC) structures was formed within 38 h of milling. However, a major FCC phase, a BCC phase, Cr23C6 carbide and an ordered BCC phase were observed after SPS. The FCC phase is enriched in Fe–Ni, the BCC phase is enriched in Ni–Al and the ordered BCC phase is especially enriched in Al, respectively. In addition, nanoscale deformation twins obviously presented only in partial FCC phase after SPS. The compressive strength and Vickers hardness of Al0.5CrFeNiCo0.3C0.2 high entropy alloy are 2131 MPa and 617 ± 25 HV, respectively.