Effect of annealing time on microstructure and corrosion behavior of CoCrFeMnNi high-entropy alloy in alkaline soil simulation solution

The effect of annealing time on the microstructure and corrosion behavior of CoCrFeMnNi HEA was explored in alkaline soil simulation solution by using electrochemical measurements, immersion test and surface analysis technology. The results show that the corrosion resistance of HEA increases first and then decreases with increasing annealing time. The corrosion behavior of HEA is related to σ-phase, grain size, inclusions and surface passive film. The σ-phase distributed at the grain boundary(GB) and the Mn-rich inclusions facilitate the pitting corrosion. Most of pits occurred in or near the GB regions are attributed to the selective dissolution of Fe, Co, and Cr elements. And the pits generated inside σ-phase are mainly caused by the selective dissolution of Cr element. While Mn element in the two inclusions is selectively dissolved, resulting in the occurrence of holes.