Atomistic study of the effect of hydrogen on dislocation emission from a mode II crack tip in alpha iron

Experimental and analytical studies have shown that the presence of hydrogen enhances dislocation emission. However, the effect of hydrogen on dislocation emission is not well understood. In this study, we investigated the effect of hydrogen on dislocation emission from a mode 11 crack in alpha iron using an atomistic model. We found that hydrogen decreases the stacking fault energy of alpha iron, resulting in an enhancement of dislocation emission. It is clarified that hydrogen atoms existing within a few angstroms of the crack tip only enhance the dislocation emission. We also confirmed that dislocation emission enhancement can occur at realistic hydrogen concentrations of hydrogen gaseous condition under thermal equilibrium conditions. (C) 2009 Elsevier Ltd. All rights reserved.