An atomistically-informed phase-field model for quantifying the effect of hydrogen on the evolution of dislocations in FCC metals

Abstract A new atomistically-informed phase-field model is developed to quantify the effect of hydrogen on the evolution of dislocations. In this model, the long-range interaction between dislocation and hydrogen is considered through the elastic interaction energy due to their eigenstrain fields, and the short-range interaction is taken into account by the hydrogen-affected dislocation core energy. The non-conserved phase-field order parameters describing the evolution of dislocations are controlled by the time-dependent Ginzburg-Landau equations, while the conserved order parameter representing the distribution of hydrogen atoms is governed by the Cahn-Hilliard diffusion equation. To explore the capability of this newly developed phase-field model, it is employed to simulate the hydrogen effect on both the static dissociation of dislocations and the dynamics shrinkage of a dislocation glide loop at zero applied stress in nickel (Ni). The simulation results show that, on the one hand, hydrogen can enhance the equilibrium spacing between two partial dislocations mainly due to the short-range interaction. On the other hand, hydrogen can impede the shrinkage of the glide loop by reducing its line energy. These results are well consistent with the atomistic calculations and theoretical predictions. It means that this new model can well capture both the hydrogen-affected dislocation dynamics influenced by long-range interaction and the hydrogen-affected equilibrium configurations of dislocations dominated by short-range interaction. Finally, with minor modifications, this new model can be further employed to study the effect of hydrogen on the evolution of various microstructures beyond dislocation networks at the mesoscale, which is crucial for a thorough understanding of the hydrogen-induced premature failure mechanisms.