Experimental and analytical studies had shown that the presence of hydrogen enhanced dislocation emission. However, the effect of hydrogen on dislocation emission was not well understood. Here, the effect of hydrogen on dislocation emission from a mode II crack in alpha iron was investigated by using an atomistic model. It was found that hydrogen decreases the stacking fault energy of alpha iron, resulting in an enhancement of dislocation emission. It was clarified that hydrogen atoms existing within a few angstroms of the crack tip only enhance the dislocation emission. It was also confirmed that dislocation emission enhancement could occur at realistic hydrogen concentrations of hydrogen gaseous condition under thermal equilibrium conditions.

Atomistic Study of the Effect of Hydrogen on Dislocation Emission from a Mode II Crack Tip in Alpha Iron. S.Taketomi, R.Matsumoto, N.Miyazaki: International Journal of Mechanical Sciences, 2010, 52[2], 334-8