Modeling plasticity of MgO by 2.5D dislocation dynamics simulations

In this study, we model the plasticity of MgO (periclase) using a 2.5-dimensional (2.5D) dislocation dynamics (DD) simulation approach. This model allows us to incorporate climb in DD simulations to model the creep behavior at high-temperature. Since a 2D formulation of DD cannot capture some important features of dislocation activity (e.g. those involving line tension), local rules are introduced to take these features into account (this is the 2.5D approach). To ensure the validity of such approach, the model is applied over a wide temperature range with a view in the lower temperature regimes where the newly introduced mechanism (climb) is not active, to benchmark our model against previous 3D simulations and experimental data. Thus we consider successfully a low temperature (T≤600 K) regime where plasticity is dominated by dislocation glide in the thermally activated regime; an intermediate regime (T=1000 K) where plasticity is dominated by dislocation-dislocation interactions; and a high-temperature regime (1500≤T≤1800 K) which is the actual goal of the present study and where creep plasticity is governed by dislocation glide controlled by recovery (climb being considered here). We show that, taking into account the range of oxygen self-diffusion coefficients available in the literature, our simulations are able to describe properly the high-temperature creep behavior of MgO.