Intermediate Temperature Fatigue Induced Precipitation and Associated Corrosion in CrMnFeCoNi High Entropy Alloy

Understanding the corrosion behavior of high entropy alloys (HEAs) after intermediate temperature fatigue is critical to prevent their catastrophic failures from the reduction of corrosion resistance. Here, we investigated the corrosion behavior of CrMnFeCoNi HEA after 500 °C fatigue test with strain amplitudes of 0.2% and 0.5%. The intermediate temperature fatigue induced two types of precipitates, which were determined as Cr-rich σ phase and NiMn-rich L1₀ phase. Higher strain amplitude not only promoted precipitates generations but also spread the nucleation sites from intergranular to both intergranular and intragranular. Furthermore, we found that the deterioration in corrosion resistance of the alloy was derived from the increase of precipitates, which destroyed the stability of the passive film. The above results revealed that intermediate temperature fatigue impaired the stabilization of the solid solution state and subsequent corrosion resistance of CrMnFeCoNi HEA, where the higher strain amplitude led to more precipitates and more severe corrosion.