Effect of Cu content on the microstructure and corrosion resistance of AlCrFeNi3Cux high entropy alloys

The FCC+B2/BCC structure of AlCrFeNi3Cux (x = 0 eutectic, x = 0.2, 0.4 hypo-eutectic, x = 0.6, 0.8, 1.0 dendritic) high-entropy alloys were fabricated and corrosion behaviours were investigated. In 3.5 wt% NaCl solution, pitting occurred initially in the B2 phases of all alloys. The values of corrosion rate, icorr and ipass first increased and then decreased with increasing Cu content. The AlCrFeNi3Cu0.4 alloy exhibited optimal corrosion resistance attributed to the increased passive film protection and reduced the volume fraction of B2 phases. The Cr-rich BCC precipitate in B2 phase generated dense Cr2O3 passive film improving localized corrosion resistance.