Effect of Al addition on phase constituent and corrosion behaviors of AlxCrFeMo0.5Ni2 high-entropy alloys

In the paper, the changes of phase constituent and corrosion resistance of AlxCrFeMo0.5Ni2 (x = 0, 0.5, 1.0, 1.5 and 2.0) high-entropy alloys (HEAs) were studied. When x = 0 and 0.5, the phase constituent of the alloys shows the dendritic (DR) phase of face-centered cubic (FCC) structure and the interdendritic (ID) phase of sigma phase. When x increases to 1.0 and 1.5, the dendritic phase transforms into an ordered B2 structure while the interdendritic phase does not change. When x increases to 2.0, the alloy is completely composed of two kinds of body- centered cubic (BCC) phases, in which the dendritic phase is not changed while the interdendritic phase transforms from the sigma phase into a disordered BCC structure. The Al2.0CrFeMo0.5Ni2 HEA exhibits the best anticorrosion capacity in the NaCl solution, with the lightest degree of galvanic corrosion due to the electric potential difference between the BCC phase and the ordered B2 phase is small and the minimum corrosion current density of 132 nA/cm2 among the studied alloys.