The effects of misfit and diffusivity on γʹ rafting in Re and Ru containing Nickel based single crystal superalloys—details in thermodynamics and dynamics

Rafting is one of the prominent features of Nickel single crystal superalloys in high temperature creep deformation, which has significant influence on creep rupture property. Some detailed comparisons were carried out to illustrate the different effects of misfit and diffusion on the rafting behavior. Its thermodynamic and kinetic processes were also discussed in the present study. Firstly, comparing with the lattice misfit, atom diffusion shown more remarkable influence on γʹ rafting in the present alloy system. Second, the misfit stress release made Gibbs free energy of γ and γʹ phases move in the opposite direction, which provided driving force for the dissolution of γʹ in horizontal channel. Thirdly, external loading could not change the fraction of γʹ phase, the dissolved part of γʹ must re-precipitated in the adjacent vertical channel powered by rafting driving force. At last, the atoms migration by diffusion were mainly occurs in the disordered γ channel, the pipe diffusion along interfacial dislocations accelerated the efficiency of atom migration for rafting.