Effects of Ni content on the corrosion behavior of Al0.5CoCrFeNix high entropy alloys in acid and alkaline media

The present work investigates the influence of Ni content on the microstructure evolution of Al0.5CoCrFeNix high‐entropy alloys followed by the study on their corrosion behavior in acid and alkaline solutions, respectively. The microscopic characterization demonstrates that the transformation from a BCC single‐phase to a triple‐phase (BCC + FCC + B2) structure occurs with the increase of Ni content. The corrosion behavior of Al0.5CoCrFeNix high‐entropy alloys was evaluated by electrochemical measurements coupled with morphology analysis. It is found that the corrosion on Al0.5CoCrFeNi0 high‐entropy alloy in both acid and alkaline media is uniform due to its homogeneous microstructure. In contrast, the increase of Ni content leads to the formation of Al, Ni enriched B2 phase with lower Volta potential, causing the respective occurrence of selective dissolution in acid and preferential oxidation in alkaline on the Al0.5CoCrFeNi0.2, Al0.5CoCrFeNi0.6, and Al0.5CoCrFeNi0.8 high‐entropy alloys.