Study of the influence of hydrogen on strain hardening and strain localization in a Fe-19Ni-24Cr austenitic steel through quantitative dislocation structure analysis

The evaluation of hydrogen's impact on key variables of dislocation structures—such as scale and boundary thickness/misorientation—in Fe-Ni-Cr austenitic steels offers deeper insight into the influence of hydrogen on deformation behavior. This understanding can aid in designing steels with enhanced resistance to hydrogen embrittlement. In this study, we examined the interplay among hydrogen, dislocation structure, strain hardening, and strain localization in a Fe-19Ni-24Cr (wt. %) austenitic steel through quantitative dislocation structure analysis. The evaluation of strain hardening by a dislocation-structure-based statistical model clarifies the individual roles of dislocation cells, cell blocks, and dense dislocation walls in the hardening process. We find that the impact of elastic shielding on key variables of dislocation structure and the hardening parameter associated with dislocation-forest hardening is limited, leading to only slight variations in hardening mechanisms. The hardening mechanism most dependent on hydrogen is solid-solution strengthening. Additionally, this study uncovers several hydrogen-related effects associated with the activation of secondary dislocation structures and strain localization at cell block boundaries, proposing a dislocation-based model that correlates the observed phenomena. These results provide a comprehensive understanding of the influence of hydrogen on dislocation-based processes controlling the deformation behavior and hardening in Fe-Ni-Cr austenitic steels.