Revealing Strengthening Contribution of Grain Refinement and Phase Precipitation in CrMnFeCoNi High-Entropy Alloy Prepared from Different Powders

Equiatomic CrMnFeCoNi high-entropy alloys (HEAs) were prepared by vacuum hot-pressing sintering with single phase precursor powders made from mechanical alloying (MA) or spray-drying (SD), respectively. MA process was found beneficial for the following precipitation and formation of secondary phases during sintering, after which multiphase bulk HEAs were formed consisting of FCC, M23C6, and precipitated nanoscale sigma phases. The tensile and compressive yield strengths of bulk HEAs fabricated from MA powders reached 1150 and 1200 MPa, respectively, which were about three times than SD powders. The excellent mechanical properties of the former were found due to the precipitation of nanoscale sigma phase and M23C6 intermetallic resulted from the MA treatment and sintering processing. Nanoscale sigma and M23C6 phase can effectively strengthen the alloy not only by self-reinforcement but also through the grain boundaries of the refined grains induced by the precipitation.