The effect of heat treatment on the microstructure of Co50Ni25Al8Ti8Nb3Ta3W3 high entropy alloy and its high-temperature oxidation resistance

Abstract

The design based on high-entropy alloys (HEAs) is undergoing a conceptual expansion from equiatomic alloys to non-equiatomic alloys. To provide the experimental basis for non-equiatomic high-entropy alloys and their oxidation resistance at high temperatures, in this study, a Co50Ni25Al8Ti8Nb3Ta3W3 high-entropy alloy was prepared by a vacuum arc melting method, and then it was subjected to different aging heat treatments. The phase composition, element composition distribution, and mechanical properties of the alloy were characterized by XRD、SEM/EDS. In addition, we have systematically studied the high-temperature oxidation resistance of the alloy and analyzed the high-temperature oxidation mechanism of the alloy. The results showed that the phase composition of the Co50Ni25Al8Ti8Nb3Ta3W3 high-entropy alloy is a single fcc solid solution phase, and the grains of the alloy become coarser after secondary aging. Many oxidation products were produced after high-temperature oxidation of the alloy. The oxidation products of the outermost layer of the alloy are mainly CoNiO2, CoTiO3, and Ni2O3, and the oxidation products of the intermediate layer are mainly Al2O3, TiO2, and Nb2O3.