EFFECT OF HYDROGEN TRANSPORTATION BY DISLOCATIONS ON HYDROGEN EMBRITTLEMENT OF MATERIALS

Hydrogen transportation by dislocation could lead to the redistribution of hydrogen atoms and aggravation of hydrogen damage in structural metals, but it lacks the support of experimental results. In this paper, the high-Mn steel fracture characteristics after hydrogen pre-charged under four strain rates (1×10^–3 s^–1, 1×10^–4 s^–1, 1×10^–5 s^–1 and 1×10^–6 s^–1) were firstly compared. Subsequently, theoretical calculations were combined to evaluate the effect of dislocation transported hydrogen on hydrogen embrittlement behaviors of metals under different strain rates. The results show that hydrogen embrittlement sensitivity and brittle area degree under the lower strain rates (1×10^–5 s^–1 and 1×10^–6 s^–1) were higher than those under the higher strain rate (1×10^–3 s^–1 and 1×10^–4 s^–1). Hydrogen atoms could move farther due to the dislocation transported hydrogen under low strain rate, resulting in a longer hydrogen movement distance and a deeper brittle zone depth. In addition, more hydrogen atoms could be enriched at the grain boundary resulting in the largest area of brittle zone in the fracture at the slowest strain rate (1×10^–6 s^–1). However, due to the formation of defects with strong binding energy of hydrogen atoms during the plastic deformation, the actual distance of dislocation transported hydrogen was much lower than the theoretical value.