Modeling hydrogen diffusion and its interaction with deformed microstructure involving phase transformation–Theory, numerical formulation, and validation

This study presents, for the first time, a model capable of simulating the complex interactions among deformation, phase transformation, and hydrogen (H) diffusion in H-charged transformation-induced plasticity (TRIP)-assisted steel. The model integrates a crystal plasticity (CP) framework with a deformation-induced martensitic transformation (DIMT) model and a H diffusion model while incorporating transformation-induced H release (TIHR). Furthermore, it accounts for H-enhanced localized plasticity (HELP) and H-enhanced phase transformation (HEPT) to capture the influence of H on mechanical behavior. The developed model is numerically implemented using the finite element method, and a series of case studies are conducted to systematically investigate the interplay between deformation, phase transformation, and H diffusion. The simulation results successfully support experimentally reported observations, demonstrating that phase transformation leads to a significant increase in H concentration within austenite and transformed martensite. This results in local oversaturation of H and anomalous diffusion, which are expected to contribute to increased susceptibility to H embrittlement (HE). These findings suggest that metastable austenite is significantly more susceptible to HE than stable austenite. Overall, the proposed model enhances the understanding of the intricate mechanisms governing H-charged TRIP-assisted steels, providing valuable insights for designing materials with improved resistance to HE.