The influence of hydrogen trapping behavior under pre-strain on the embrittlement behavior of α-Fe at a high strain rate

Abstract

This study employs molecular dynamics (MD) simulations to investigate hydrogen (H) trapping behavior in pre-strained single-crystal α-Fe, and the role of H atoms and H cluster structures in influencing strength degradation and void evolution is further clarified. The results show that compressive pre-strain suppresses H diffusion and enhances trapping efficiency, while tensile pre-strain accelerates diffusion but reduces trapping. Quantitative analysis reveals that the proportion of aggregated H atoms (Pagg_H) is closely correlated with material strength degradation (∆σ), which proceeds through three stages: random H introduction → H cluster nucleation → H cluster growth. H cluster nucleation dominates strength degradation by introducing anisotropic stress into the matrix, intensifying local stress/strain gradients and weakening the influence of pre-strain on strength. Compared with isolated H atoms, the decohesion effect of H clusters increases with cluster size. Moreover, H clusters significantly reduce the critical void-nucleation pressure (Pn) and promote void nucleation at H cluster sites, thereby making damage evolution jointly governed by void competition and H cluster effects.