Early Stages of Crack Nucleation Mechanism in Fe39Mn20Co20Cr15Si5Al1 High-Entropy Alloy during Stress Corrosion Cracking Phenomenon: Pit Initiation and Growth

This study investigated the susceptible sites for pit nucleation in a transformation-induced plasticity (TRIP) Fe39Mn20Co20Cr15Si5Al1 (at.%) high-entropy alloy (HEA) in 3.5 wt.% NaCl solution. The investigation involved a constant-load stress corrosion cracking (SCC) experiment. The SCC testing was interrupted at different pre-determined time intervals to characterize the specimen surface using a scanning electron microscope (SEM), electron backscattered diffraction (EBSD), and a three-dimensional optical stereomicroscope. The EBSD results revealed pit nucleation at the susceptible γ–ε interphase and ε–ε interlath/plate boundaries. The three-dimensional profile and SEM results indicated an increase in pit depth with no change in pit diameter on the surface of the specimen as the experiment progressed over time. This study highlights the importance of microstructural features and mechanical loading in the corrosion behavior of TRIP HEAs, providing insights into the mechanisms of pit nucleation and growth under aggressive environmental conditions.