Revealing the oxidation behavior of AlCrxFeNi lightweight multi-principal element alloys via experimental and first-principles calculations

Developing alloys capable of withstanding high temperatures is crucial for modern engineering applications. Introducing multi-component alloys (MPEAs) has provided new strategies for designing high-temperature alloys. We have successfully prepared a series of AlCr _xFeNi lightweight MPEAs in this study. The oxidation behavior of AlC _xFeNi lightweight at 800 °C was investigated systematically through a combination of experimental methods and first-principles calculations. The microstructure characterization before oxidation reveals that the lightweight AlCr _xFeNi MPEAs consist of BCC and B2 phases. In contrast, the AlCrFeNi alloy exhibited a microstructure characterized by typical eutectic features. Oxidation tests indicate that all three alloys exhibited oxidation kinetics following a parabolic law, with oxidation rates decreasing as the Cr content increased. Post-oxidation microstructural characterization revealed an oxide layer composed primarily of Al ₂O ₃ and Cr ₂O ₃ on the alloy surfaces. First-principles calculations provided insights into the microscopic mechanisms underlying the oxidation process. The results demonstrate that the adsorption energy of the O atom at the top position of the Cr atom is significantly lower than that of the Al atom at the top position. Electronic structure analysis shows that the Cr-O covalent bonding is stronger than the Al-O covalent bonding, which accounts for the oxidation resistance improvement as the Cr element content increases. This study advances MPEAs for high-temperature environments by elucidating these microscopic mechanisms.