Influence of grain boundary energy on hydrogen segregation tendencies

Hydrogen-induced ductility loss is a major limitation to the durability of structural alloys, which arises from interactions between H and microstructural defects such as grain boundaries and alters local deformation mechanisms. To describe these interactions, it is crucial to determine the distribution of interstitial H across various grain boundary types; however, probing H location at grain boundaries is experimentally challenging even at room temperature due to significant dynamic H redistribution. Here, we develop and apply an atomistic model combining molecular dynamics and grand canonical Monte Carlo sampling to elucidate H-segregation in polycrystals. First-principles calculations were performed to validate the performance of interatomic potentials in predicting the stability of grain boundaries and their H affinity. Polycrystalline samples with 27 randomly oriented grains were simulated to examine H–grain boundary interactions as a function of H concentration and grain boundary misorientation angle. The analysis revealed a strong dependence of H-segregation on the grain boundary energy. This study provides a foundation for modeling H incorporation in structural alloys and for ensuing studies of deformation mechanisms in an effort to mitigate embrittlement.