Coupling phase field and viscoplasticity to study rafting in Ni-based superalloys

An elasto-viscoplastic model is developed to study the microstructural evolution during creep loading in a model AM1 superalloy. Elastic anisotropy and inhomogeneity, as well as the description of long-range order in the gamma' phase, are included in the model. Plastic activity is introduced using a continuum crystal plasticity framework at the mesoscale. Special attention is paid to the corresponding parameter identification from experiments. Two-dimensional simulations of creep in the [100] direction are performed, and the results are compared to the predictions of an elastic phase field model, in order to characterize the influence of plastic activity on the microstructural evolution. In particular, our simulations show that plastic activity in the gamma channels significantly increases the rafting kinetics and allows misalignments of rafts with respect to cubic directions. The simulation results are critically discussed and improvements to the model are proposed.