Phase-field modeling of coring structure evolution in Pu–Ga alloys

During casting of Pu–Ga alloys, the huge difference in Ga diffusivity in ε (body centered cubic) and δ (face centered cubic) phases results in the formation of coring structures which consist of Ga-rich cores with Ga-poor edges. The elastic interaction among different oriented δ grains, matrix ε and diffusive Ga atoms may lead to a directional diffusion and δ grain growth. A phase-field model for modeling the coring structure evolution and Ga homogenization kinetics in three dimensions is developed. The effects of diffusivity inhomogeneity, internal stresses and cooling rate on the coring structure evolution are studied.