Phase-field modeling of bimodal microstructures in nickel-based superalloys Original Research Article

The phase-field approach is used to study the formation and ageing of bimodal microstructures in a model Ni-based superalloy. Particular attention is paid to the definition of interfacial energies in the presence of elastic strain fields and to the incorporation of these energies in the phase-field formalism. During a two-step annealing procedure, our model predicts the formation of large anisotropic image precipitates (called secondary precipitates) and small, almost isotropic image precipitates (called tertiary precipitates). Finally, the phase-field model is used to characterize the ageing of tertiary precipitates. In agreement with experiments, we show that the mean size of the tertiary precipitates first grows as image and finally reaches a plateau. This peculiar behavior is explained using phase-field simulations with prescribed geometries and with the development of a simple analytic model.