High-Temperature Oxidation Behavior of AlCoCrCuFeNi High-Entropy Alloys Prepared by Selective Laser Melting

AlCoCrCuFeNi high-entropy alloys (HEAs) were prepared by selective laser melting (SLM). The microstructure and high- temperature oxidation behavior at 800, 1000 and 1200 degrees C were studied. The phase composition and morphological characteristics of the oxide film were analyzed by XRD and SEM. The results indicate that the prepared AlCoCrCuFeNi HEAs mainly contain bcc phase, bcc/B2 phase and a small amount of fcc phase, and the microstructure is a non-equilibrium heterostructure composed of long straight columnar dendrite and equiaxed cell structures. The HEAs have good oxidation resistance at different temperatures. The oxidation kinetics curves basically follow the parabolic law. The oxidation rate exhibits a clear dependence on temperature, which increases with the increase in temperature, and obvious voids and cracks appear in the oxide films, which provide channels for diffusion of elements to aggravate the oxidation reaction; as a result, (t)he oxide film peeling becomes more and more serious. The main components of the oxide films are Cr2O3, Al2O3 and spinel MCr2O4 mixed oxides. The denser oxide film can effectively inhibit the matrix from being further oxidized and improve the anti-oxidation properties of SLMed HEAs.