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

ZQ Zheng and S Liang and MS Huang and L Zhao and YX Zhu and ZH Li, MECHANICS OF MATERIALS, 173, 104443 (2022).

DOI: 10.1016/j.mechmat.2022.104443

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 gamma-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 crit-ical nucleation stress of the Frank-Read source are obtained, which can further serve upscaled dislocation dy-namics simulation and dislocation-density based crystal plasticity modelling.

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