Effect of Y additions on the oxidation behavior of vacuum arc melted refractory high-entropy alloy AlMo0.5NbTa0.5TiZr at elevated temperatures

The effects of yttrium (Y) addition on the oxidation resistance of AlMo0.5NbTa0.5TiZr refractory high entropy alloys (RHEAs) were investigated. The oxidation consists of the formation of passivating and complex oxide layer and the volatile oxidation of Mo, resulting in a power-law dependence of weight gain throughout the early stage of oxidation. Y addition induced the formation of continuous AlNbO4-based oxidation scales and reduced the volatile oxidation of Mo. The pegs-oxidized Y formed in the interfaces between oxide and substrate improved the adherence of the oxide scale. The high content of Y was disadvantageous to resisting oxidation at high temperature.