Effect of grain size on the corrosion resistance of the Fe41Mn25Ni24Co8Cr2 high entropy alloy

The annealing effect on the corrosion resistance of a non-equiatomic Fe41Mn25Ni24Co8Cr2 high entropy alloy after high-ratio differential speed rolling was examined. The corrosion resistance of the alloy improved as the grain size decreased within the grain-size range of 3.5 µm to 84.9 µm. Grain boundaries were identified as contributing factors to the enhanced corrosion resistance by acting as barriers to corrosion pitting by inducing changes in crystallographic orientation. Additionally, grain boundaries facilitated the transportation of Cr ions to the surface by providing a pathway with a higher diffusivity and provided the nucleation sites of Cr oxide, leading to the formation of a more compact and evenly distributed corrosion layer on the surface of the alloy with a smaller grain size.