Nonlinear chemomechanical modeling of hydrogen diffusion in super duplex stainless steel and comparison with x-ray diffraction measurements

A coupled hydrogen (H) diffusion and higher-order strain gradient plasticity model is used to predict H localization in the ferrite ( α ) and austenite ( γ ) phases of super duplex steel under plane stress conditions. The geometry and finite element (FE) mesh are derived from optical micrograph images of the phase morphology, ensuring a realistic representation of the alloy’s microstructure. The model highlights the role of individual phases in coupled diffusion–mechanics interactions and demonstrates that the phase morphology significantly impacts the localization of H in the material. The results indicate that plastic strains in the ferrite phase exert a much greater influence on the spatial distribution of H than in the austenite phase. Finally, results of the model compare well with in situ X-ray diffraction (XRD) measurements of the temporal evolution of the strain induced by H charging. These findings provide valuable insight for future alloy design strategies aimed at mitigating H localization and preventing embrittlement. • Developed a fully coupled strain gradient plasticity–hydrogen diffusion framework for super duplex stainless steel. • Constructed a realistic two-phase microstructure using optical micrographs to generate the FE geometry and mesh. • Achieved good agreement between predicted hydrogen-induced strain evolution and XRD measurements, and between simulated hydrogen penetration depth and SEM fractography observations. • Demonstrated that the plastic strain and stress heterogeneity govern hydrogen localization.