Large-scale three-dimensional phase field simulation of gamma '-rafting and creep deformation

Three-dimensional phase field simulations of coupled gamma/gamma' microstructural evolution and plastic deformation in single crystal Ni-Al are carried out at micrometer scales. Coherent gamma/gamma' microstructures and plastic deformation in gamma-channels are described using a single, consistent methodology based on Khachaturyan's phase field microelasticity approach to coherent precipitates and dislocations. In particular, a new set of phase fields is introduced to characterize local density of dislocations from individual active slip systems. To increase the length scale of the phase field simulations, the Kim-Kim-Suzuki (KKS) treatment of gamma/gamma' interfaces was adopted. The rafting kinetics, precipitate-matrix inversion process and the corresponding creep deformation are characterized with respect to parameters such as applied stress and lattice misfit. The simulation results on gamma'-rafting kinetics and morphological evolution of the gamma/gamma' microstructures are compared with available experiment. The model can be used to carry out parametric studies of the effects of material and processing parameters such as alloy composition, external stress and working temperature on gamma'-rafting kinetics, morphological evolution and the corresponding creep deformation.