The effect of the grain refinement on the corrosion resistance of the CoCrNi medium-entropy alloy in chloride solution

The ratio of the twin decreased after thermomechanical process for the CoCrNi medium-entropy alloy. The grain refinement decreased the passive current and increased the breakdown potential of the CoCrNi medium-entropy alloy in sodium chloride solution. The electrochemical impedance spectroscopy analysis showed that the grain refinement of the CoCrNi medium-entropy alloy facilitated to form thicker passive films and larger passive film resistance, which thus resulted into better corrosion resistance in sodium chloride solution. More nucleation sites after the grain refinement could enhance diffusion rate of alloying element and promote to form thicker and more stable passive films on refined grain CoCrNi medium-entropy alloy. Moreover, sufficient recrystallization level within refined grains for the CoCrNi MEA also improved its corrosion resistance.