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 AlMo 0.5 NbTa 0.5 TiZr 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 AlNbO 4 -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. • 0.6 at.% Y addition makes the AlMo 0.5 NbTa 0.5 TiZr RHEA possess a better oxidation resistance at 800–1000 °C. • Y addition induces the formation of continuous AlNbO 4 -based complex oxidation scales over the dendritic regions. • The pegs-oxidized Y formed in the interfaces of oxide and metal could improve the adherence of the oxide scale.