Effects of Non-Equilibrium Solidification and Aging Treatment on Microstructure Characteristic of a Ni-Base Superalloy

Copper mould spray casting and aging treatment were performed to investigate the microstructure evolution of a Ni-base superalloy. With increasing the cooling rate during solidification, the morphology of primary γ phase changes from coarse dendrite to fine dendritic structure with radial-like feature, accompanied by the inhibition of γ′ phase due to the shortened period during the subsequent solid state transformation process. After aging treatment, both the size and volume fraction of γ′ phase are increased with prolonging the isothermal time, which generate the morphology transition of precipitates from irregular and spherical to ellipse and rectangle due to the competition between the interface energy and strain energy.