Influence of external stress and plastic strain on morphological evolution of precipitates in Ni-based superalloys

An analytical method is proposed to investigate the morphological evolution of γ′γ′ precipitates in Ni-based superalloys. Two types of superalloys are considered with different ratio between the Young’s moduli of the precipitates and the matrix. Based on Eshelby’s equivalent inclusion theory and Mori–Tanaka’s mean field method the elastic energy is calculated as a function of the particle shape. The plastic strain induced by the formation of dislocation networks at the phase interface is taken into account. The results show that the external stress and the plastic matrix strain play a significant role for shape stability and the rafting mechanism of the precipitates. The elastic–plastic analysis provides a satisfactory explanation for all available experimental observations superalloys undergoing plastic creep.