A dislocation dynamics-assisted phase field model for Nickel-based superalloys: The role of initial dislocation density and external stress during creep

The effect of initial dislocation density and external stress on primary creep of Nickel-based superalloys are studied by a combined continuum dislocation dynamics/phase-field model. This model can simultaneously predict the dislocation motion as well as the γ/γ' evolution and yields macroscopic creep properties as a natural outcome - all of which are supported by experimental data. The rafting simulation results show that the initial dislocation density as well as the external stress can dramatically influence the aspect ratio of the γ' precipitates and the interface dislocation density at the γ/γ' interfaces. In contrast, the plastic strain towards the end of primary creep is not sensitive to the initial dislocation density due to a seeming strain rate inversion during creep, and it is dependent on the applied external stress.