Microstructural evolution and high-temperature oxidation resistance of laser-modified AlCoCrFeNi(YHf) high-entropy alloy at 1200 °C

The Y/Hf-doped equiatomic AlCoCrFeNi high-entropy alloy (HEA) shows good oxidation resistance but suffers from Al depletion and oxide layer spallation during long-term exposure at 1200 °C. In this study, nanosecond laser remelting was employed to regulate the surface microstructure and diffusion behavior of the alloy. Results showed that laser remelting introduced a high density of lattice defects and improved Al homogenization. This accelerated elemental diffusion and oxidation of Fe, Cr and Al. Furthermore, the oxidation behavior shifted from competitive oxidation to a selective Al 2 O 3 -dominated mode quickly, leading to the formation of a dense and adherent protective scale. In contrast, the original alloy formed the oxide layer more slowly, resulting in enhanced internal oxidation and deteriorated oxidation resistance during prolonged exposure. As a result, the laser-modified alloy exhibited a significantly reduced oxidation rate and enhanced oxidation resistance at 1200 °C. This work demonstrates that nanosecond laser remelting is an effective strategy to improve the oxidation resistance of HEAs.