Effects of Mo and Nb on the microstructure and high temperature oxidation behaviors of CoCrFeNi-based high entropy alloys

摘要: A series of CoCrFeNi(Mo, Nb) high entropy alloys (HEAs) were prepared using vacuum arc-melting. The effect of Nb and Mo on the microstructure and high temperature anti-oxidation properties of HEAs was investigated. The addition of only Mo was found to not cause formation of new phase, but did increase the lattice distortion. After the addition of Nb, as-prepared CoCrFeNiMo0.2Nb0.1 and CoCrFeNiMo0.2Nb0.2 alloys are characteristic of duplex-phase structures of FCC and Laves, in which the Laves phase is semi-coherent with FCC matrix. Our studies also revealed that the oxidation kinetics of the alloys followed parabolic rate law and the corresponding oxidation rate constants were calculated. Due to the synergistic effects of Mo and Nb, the anti-oxidation properties of HEAs improved significantly. It was also discovered that the new Laves phase containing Mo and Nb at the inner oxidation layer hindered the …