Studying the effects of hydrogen on dislocation mobility and multiplication in nickel by phase-field method

Abstract

The effects of hydrogen on dislocation mobility and operation of the Frank-Read source are evaluated using our recently developed phase-field model. This is achieved by accounting for long-range elastic hydrogen-dislocation interaction (i.e., hydrogen shielding effect) and short-range inelastic hydrogen-dislocation core interaction through atomically informed generalized stacking fault energy (GSFE, or γ-surface). The results show that, due to the short-range interaction, hydrogen impedes the dislocation motion, which is contrary to the long-range hydrogen shielding effect. The bow-out configurations of the Frank-Read source obtained by the phase-field model can agree well with that from the atomic simulations. Hydrogen can decrease the critical nucleation stress of the Frank-Read source and thus enhance the hydrogen-induced plasticity. Moreover, the hydrogen-induced dislocation core energy reduction prevails over the hydrogen-induced elastic shielding, especially when the hydrogen concentration is low. Our results suggest that the modification of the dislocation core structure due to the short-range interaction plays an important role in understanding the hydrogen-enhanced localized plasticity mechanism. Finally, quantitative influences of hydrogen on dislocation mobility and critical nucleation stress of the Frank-Read source are obtained, which can further serve upscaled dislocation dynamics simulation and dislocation-density based crystal plasticity modelling.