Effect of Al content on high temperature oxidation resistance of AlxCoCrCuFeNi high entropy alloys (x=0, 0.5, 1, 1.5, 2)

The oxidation behavior of AlxCoCrCuFeNi (x = 0, 0.5, 1, 1.5, 2) high entropy alloys are discussed in this work. Five kinds of HEAs with nominal compositions of are prepared by vacuum arc melting and subjected to isothermal oxidation at 1000°C for 100 h in static air. The results indicate that three typical CuNi-rich, AlNi-rich and matrix phases emerge after oxidation. In all oxidized HEAs there is a tendency to generate the Cr depletion or Al depletion region directly beneath the oxidation layer. With the increase of Al content, the oxidation scale mainly consists of alumina instead of Cr2O3 and the parabolic rate constant of Al2CoCrCuFeNi HEA reaches the minimum value, which clarifies the superior high temperature resistance.