Microstructure, Mechanical Properties, and High-Temperature Oxidation Behavior of Al0.3CoCrFeNiWx High Entropy Alloys

A series of Al0.3CoCrFeNiWx (x=0, 0.2, 0.3, and 0.5) high entropy alloys were designed. The effect of W addition on microstructure, mechanical behavior, and high-temperature oxidation was systematically investigated. It is indicated that the addition of W element promoted the structural transformation of as-cast Al0.3CoCrFeNiWx HEAs from single FCC to FCC + mu, and the volume fraction of mu phase increased as the W content increased. The yield strength of the alloys was enhanced with increasing W content, which could be attributed to solid solution and second phase strengthening. Oxidation studies were performed on the HEAs at 800 degrees C for 100 hours. Protective external Cr2O3 layer and internal Al2O3 formed in the investigated HEAs. With increasing W content, a higher mass gain was obtained. This could be explained by the relatively decreased Cr content in the as-cast alloy as well as the depletion of Cr element in the underlying alloy caused by mu phase. The results in our work could provide clues for the development of new HEAs.