Effects of Local Segregation on Stacking Fault Energy, Hydrogen Diffusion and Dislocation Motion in Austenitic Stainless Steel: A Molecular Dynamics Study

Local chemical heterogeneity is a typical feature of selective laser melted (SLM) austenitic stainless steel and is closely related to its hydrogen-assisted deformation behavior. In this work, molecular dynamics simulations are performed to investigate the effects of local segregation on stacking fault energy, hydrogen diffusion, and dislocation motion in austenitic stainless steel. Three representative alloy compositions, Fe71Cr17Ni12, Fe71Cr23Ni6, and Fe71Cr11Ni18, are used to describe local composition variation associated with segregation in SLM-relevant austenitic stainless steel. The results show that Ni-rich regions exhibit relatively higher stacking fault energy and faster hydrogen diffusion, whereas Cr-rich regions show lower stacking fault energy and reduced hydrogen mobility. Hydrogen further decreases the stacking fault energy in all three alloy models and exerts a stronger influence on local defect energetics than composition variation alone. Shear simulations indicate that elemental segregation itself has only a limited direct effect on dislocation motion, whereas its interaction with hydrogen leads to a more evident retardation of partial dislocation propagation within the segregation region. These findings highlight the coupled roles of local composition variation and hydrogen in governing defect evolution and local deformation behavior in segregation-containing regions.