Microstructure and atmospheric oxidation behavior of CrCuFeMnNiCo_x high‐entropy alloys fabricated by vacuum hot‐press sintering

Abstract

The CrCuFeMnNiCox high‐entropy alloys (HEAs) were prepared by vacuum hot‐press sintering. The microstructure and atmospheric oxidation behavior at 800°C were studied. The phase structure of the Co0 alloy comprised the Cr‐rich FCC1 major phase, Cu‐rich FCC2 secondary phase, and a small amount of intermetallic compound ρ phase when x = 0. The bulk alloys comprised FCC2 major and FCC1 secondary phases when x ≥ 0.5. The oxidation kinetics curves approximately followed the parabolic law. A high Co content leads to a large oxidation weight gain of the alloys. The oxidation weight gain of the Co0 alloy was the smallest at approximately 4.46 mg cm−2 after atmospheric oxidation for 50 h, while the oxidation weight gain of the Co2.0 alloy was the largest at approximately 5.94 mg cm−2. The Co0 alloys exhibited the best oxidation resistance. Therefore, Co is not beneficial to the improvement of the oxidation properties of the CrCuFeMnNiCox HEAs. The main oxidation products of the HEAs mainly comprised MO, M2O3, M3O4, and (M,Cr)3O4 type metal oxides. The main oxidation mechanism was selective oxidation.