Effect of Co content on the phase transition and magnetic properties of Co CrCuFeMnNi high-entropy alloy powders

CoxCrCuFeMnNi (x = 0.5, 1.0, 1.5, 2.0 mol) high-entropy alloy (HEA) powders were synthesized by mechanical alloying (MA). The effects of milling time, Co content, and vacuum annealing on the structural evolution, thermostability, and magnetic properties were investigated. After 50 h of milling, the Co0.5CrCuFeMnNi HEA powder consisted of a major face-centered cubic (FCC) phase and minor body-centered cubic (BCC) phase, whereas the other three HEA powders were composed of single FCC phase. The Co0.5CrCuFeMnNi HEA powder was composed of FCC1, FCC2, and minor ρ phases when annealed at 700 and 800 °C and then completely transformed into FCC1 and FCC2 phases at 900 °C. For the other three HEA powders, the single FCC phase transformed into the FCC1 and FCC2 phases during annealing at 700–900 °C. Both increasing Co content or prolonging balling time can improve the soft magnetic properties of HEA powders. Therefore, the Co2.0CrCuFeMnNi HEA powder with a maximum saturated magnetization of 52 emu/g and a minimum coercivity of 14 Oe exhibited the best soft-magnetic properties among the four HEA powders.