Phase transformation-mediated high-temperature oxidation in an AlCrFeCoNi2.1 EHEA alloy at elevated temperature

Abstract

The oxidation behavior of an AlCrFeCoNi2.1 eutectic high-entropy alloy (EHEA) at 800 ℃ in air was meticulously examined. Under steady-state oxidation conditions, the oxide scale predominantly features a continuous and dense Al2O3 layer, interspersed with blocky Fe2O3 and Cr2O3 formations. Beneath the original surface, a single FCC matrix layer emerges due to a phase transition from BCC to FCC, driven by the extensive consumption of Al in the formation of Al2O3. This unique duplex-layer structure, comprising an Al2O3-based oxide scale and an Al-depleted FCC matrix layer, markedly enhances the oxidation performance of the alloy.