Abnormal trapping of hydrogen in the elastic stress field of dislocations in body-centered cubic iron

Abstract

It has been widely accepted that the tetrahedral interstitial site is the normal lattice trapping site for H atoms in the body-centered cubic iron. In this work, we found H trapped in a tetrahedral site is unstable in the dislocation elastic stress field. By contrast, the octahedral site is energetically preferred. This abnormal trapping phenomenon was rooted in the H-dislocation elastic interaction and zero-point quantum vibration of the H atom. At the abnormal trapping state, the interaction between H-edge dislocation and H-screw dislocation was identified to be at a similar level. As a result, the diffusivity of H around dislocation is enhanced by the abnormal trapping, and the local H content is much higher than the prediction with the assumption of normal trapping. Our results suggest that the dislocation motion can shuffle the trapping position of H atoms and assist the immature failure in the hydrogen environment.