Modeling Martensitic Phase Transformation of Retained Austenite Under Rolling Contact Fatigue

Retained austenite (RA) undergoes strain-induced martensitic transformation under rolling contact fatigue (RCF), which significantly influences the material's fatigue properties. This study investigates the transformation of RA into martensite under RCF loading using a crystal plasticity model coupled with martensitic transformation theory. To examine the effect of RA content on transformation behavior, materials with three different RA levels (5%, 15%, and 23%) were tested and simulated. The results indicate that martensite transformation initiates in the subsurface region, approximately 60 μm beneath the surface, and progresses rapidly during the early stages of cyclic loading. The martensite transformation is closely associated with active dislocation activity. The transformation rate strongly depends on the initial RA content, with higher RA levels leading to faster and deeper transformation. A strain threshold is identified, beyond which the transformation rate stabilizes and eventually saturates. Additionally, crystal orientation significantly influences martensitic transformation, with certain grain orientations being more susceptible to phase change. The simulation results clearly capture the evolution of martensitic transformation and show strong agreement with experimental observations.