Multiscale modeling of hydrogen enhanced homogeneous dislocation nucleation

Abstract A multiscale approach is proposed to predict how the presence of hydrogen influences the onset of homogeneous dislocation nucleation (HDN) and thus of plasticity. The model takes inputs that can be solely obtained from atomistic calculations, such as dislocation core structure, stacking fault energy and hydrogen–hydrogen interaction. The equilibrium hydrogen concentration around the dislocation loop is calculated using a recently developed self-consistent iterative method [1]. The complex nature of the dislocation field, as well as the equilibrium hydrogen concentration around the loops, is taken into account. The onset of HDN as a function of bulk hydrogen concentration and temperature is quantitatively predicted and is consistent with nano-indentation experiments on hydrogen loaded samples. Applying the approach to Ni, we find that even low hydrogen concentrations of about 1 at-% result in largely reduced HDN energy barriers and thus largely reduce the critical shear stress.