Micromechanical and Macroscopic Modelling (MMM)
45-degree rafting in Ni-based superalloys: A combined phase-field and strain gradient crystal plasticity study
M. A. Ali, W. Amin, O. Shchyglo, I. Steinbach.
International Journal of Plasticity, 128, 102659, (2020)
45° rafting of Ni-based superalloys has been investigated with the help of creep test simulations applying a strain gradient crystal plasticity model coupled to the multi-phase field method. This mode of rafting lies in between P- and N-type rafting modes. The model parameters are calibrated against experimental data for N-type rafting under high temperature and low stress creep condition. By increasing the stress level, the mixed-mode rafting of precipitates with a clear tendency toward formation of 45° rafts is observed. We show that the key factor for the occurrence of this type of rafting is the generation of highly localized creep strain of more than 10% due to non-homogeneous creep deformation in the form of slip bands. We have successfully captured the evolution of microstructure under high stress leading to production of localized shear bands.
Keyword(s): superalloys; dislocations; rafting;directional coarsening; phase field; crystal plasticity