Oxidation behavior of AlCoCrFeNiSix high-entropy alloys at 1100 ℃

Abstract AlCoCrFeNiSix high-entropy alloys containing different Si contents (x = 0, 0.2, 0.5, 0.8, 1.0 in molar ratio) were prepared by vacuum arc-melting. The microstructure and oxidation behavior of these alloys at 1100℃ for 200 h were investigated. After adding Si, the alloys mainly consist of BCC and Si-rich precipitates, and both the size and quantity of the Si-rich precipitates increase with increase in the Si content. A suitable content of Si in the alloys improves the oxidation resistance for promoting the formation of a dense single Al2O3 scale, while excessive Si imposes an adverse effect by forming easy-peeling scales composed of Al2O3 outer layer and mixed oxides inner layer. Formation and failure mechanisms of the oxide scales on these alloys during oxidation have been discussed.