Microstructure and oxidation behavior of the Y/Ta/Hf co-doped AlCoCrFeNi high-entropy alloys in air at 1100 ℃

The grain morphology and oxidation behavior of the Y/Ta/Hf co-doped AlCoCrFeNi high-entropy alloy (HEA) were investigated in air at 1100 ℃. The Y/Ta/Hf co-doped significantly improves the high-temperature oxidation resistance of the alloy. Hf doped AlCoCrFeNiYTa HEA presents the larger grain sizes of Al2O3, which effectively reduces the inward diffusion of O along the grain boundaries. In addition, Y/Ta/Hf co-doped AlCoCrFeNi HEA accelerates the transformation metastable Al2O3 to α-Al2O3. The oxide pegs formed at the oxide/substrate interface have a positive effect on improving the adhesion of the oxide scale, and Ta increased the probability of oxide peg formation.