The effect of interdendritic spinodal decomposition on the corrosion resistance of CoCrFeNiAl 0.5 high entropy alloy in supercritical CO 2 environment

The spinodal decomposition leads to interdendritic BCC phase in CoCrFeNiAl 0.5 HEA decomposed into BCC 1 phase rich in (Fe, Cr) and BCC 2 phase rich in (Ni, Al). The precipitation phase or basket structure generated by spinodal decomposition were critical to synergistically improving the strength and plasticity. This study investigated the effect of spinodal decomposition on corrosion resistance of CoCrFeNiAl 0.5 HEA in high -temperature supercritical CO 2 environments. The results showed that after 800 h of corrosion, the oxide on the surfaces of FCC and BCC 1 phases was both Cr 2 O 3 , while the oxide on the surface of BCC 2 phase was dense Al 2 O 3 . The interface between dendrites and interdendrite transformed into FCC/BCC 2 with spinodal decomposition. The continuous and dense Al 2 O 3 film avoids the occurrence of grain boundary corrosion. Therefore, spinodal decomposition on interdendritic BCC phase improved the corrosion resistance of CoCrFeNiAl 0.5 HEA in supercritical CO 2 environments.