Hydrogen effects on the mechanical behaviour and deformation mechanisms of inclined twin boundaries

It has been observed that coherent twin boundaries (CTBs) are resistant to hydrogen embrittlement (HE). However, little is known about the role of inclined twin boundaries in the H-related deformation and failure. Here we comprehensively investigate H segregation and its influence on the mechanical behaviour and deformation mechanisms of inclined Σ3 twin boundaries at inclination 0°≤Φ ≤ 90° using molecular dynamics simulations. Our results demonstrate that for Φ = 0° CTB and Φ = 90° symmetric incoherent twin boundary (SITB), the presence of H reduces the yield stress required for dislocation nucleation under uniaxial tension, while for inclined twin boundaries (0°<Φ < 90°), the yield stress increases with increasing H concentration. Under shear deformation, solute H increases the critical shear stress for the SITB and inclined twin boundaries (0°<Φ < 90°). The underlying deformation mechanisms are directly associated with H-modified atomic structure and GB motion. These findings deepen our understanding of the HE mechanisms of inclined twin boundaries, and provide a pathway for designing materials with high HE resistance.