γ′ rafting in single crystal blade alloys: A simulation study

Abstract

A phase field model is developed to simulate γ′ rafting in single crystal Ni–Al under the influence of external stress. Lattice and modulus mismatch between the γ and γ′ phases and γ channel plasticity are considered simultaneously in the model. To increase the computational efficiency, an average plastic strain is introduced to describe the channel plasticity based on experimental observation of dislocation density. With the elastic moduli of both phases and their lattice misfit at the aging temperature from direct experimental measurement, and thermodynamic and mobility data from available databases as inputs, the simulation results show that the type of rafting is determined by channel plasticity while modulus mismatch between the precipitate and the matrix affects only the kinetics of the rafting process. The model can be used to quickly estimate the type of rafting and, more importantly, the time when rafts fully develop.