The influence of Co content on the microstructure and corrosion behavior of Al0.3CoxCrFeNi (x = 0.25, 0.5 and 1.0) highentropy alloys were investigated. The results indicated that the increased content of Co improve the corrosion resistanceof alloy, which can be attributed to the distinction of phase composition in alloys caused by different Co content. TheAl0.3CoxCrFeNi alloy shows a double-phase (FCC + BCC) structure for x = 0.25 and 0.5, and BCC phase consists of (Al,Ni)-rich B2 phase and (Cr, Fe, Co)-rich A2 phase. The increase of Co content induces the transformations of crystalstructuresfrom BCC to FCC, resulting in the decrease of BCC phase proportion. The Al0.3CoCrFeNi alloy exhibits thesingle FCC structure, and all elements tend to be homogeneously distributed. The difference in the potential of FCC andBCC phases indicates the BCC phase acts as anode resulting to localized corrosion, while B2 phase preferentially dissolvescompared to the A2 phase due to the lower potential. Therefore, the existence of selective corrosion is found in thealloys with double-phase, by contrast, the alloy with single FCC phase shows random pitting corrosion.
The influence of Co content on the microstructure and corrosion behavior of Al0.3CoxCrFeNi (x = 0.25, 0.5 and 1.0) highentropy alloys were investigated. The results indicated that the increased content of Co improve the corrosion resistanceof alloy, which can be attributed to the distinction of phase composition in alloys caused by different Co content. TheAl0.3CoxCrFeNi alloy shows a double-phase (FCC + BCC) structure for x = 0.25 and 0.5, and BCC phase consists of (Al,Ni)-rich B2 phase and (Cr, Fe, Co)-rich A2 phase. The increase of Co content induces the transformations of crystalstructuresfrom BCC to FCC, resulting in the decrease of BCC phase proportion. The Al0.3CoCrFeNi alloy exhibits thesingle FCC structure, and all elements tend to be homogeneously distributed. The difference in the potential of FCC andBCC phases indicates the BCC phase acts as anode resulting to localized corrosion, while B2 phase preferentially dissolvescompared to the A2 phase due to the lower potential. Therefore, the existence of selective corrosion is found in thealloys with double-phase, by contrast, the alloy with single FCC phase shows random pitting corrosion.