Temperature-dependent oxidation behavior of Y-Hf co-doped and Co-free Al16Cr20Fe20Ni44 eutectic multi-principal elements alloy at 1100–1300 °C

Eutectic multi-principal elements alloys (EMPEAs) are promising candidates for high-temperature applications due to their exceptional mechanical properties and thermal stability. Herein, the temperature-dependent oxidation behavior of a Y-Hf co-doped Co-free Al₁₆Cr₂₀Fe₂₀Ni₄₄ EMPEA in the temperature range between 1100 and 1300 °C is investigated. The oxidation product is exclusively Al₂O₃ scale with the columnar grain microstructure in this temperature range, indicating that inward O diffusion plays a more critical role than Al diffusion, consequently leading to a small oxidation rate. At 1100–1200 °C, the EMPEA exhibits superior oxidation resistance due to the higher Al activity and lower reactive element (RE) in the Al-depleted layer, while the smaller coefficient of thermal expansion (CTE) minimizes residual stress. However, the EMPEA shows inferior oxidation resistance at 1300 °C, likely because the inherent softness degrades the interfacial instability under elevated thermal stress, leading to oxide scale spallation. All in all, the Y-Hf co-doped Co-free Al₁₆Cr₂₀Fe₂₀Ni₄₄ EMPEA has large potential in high-temperature applications and offers a cost-effective alternative with sustained performance stability up to 1200 °C.