Void nucleation and growth in irradiated polycrystalline metals: a phase-field model

We present a phase-field model for void formation in polycrystalline metals with vacancy concentrations exceeding the thermal equilibrium values. By incorporating a coupled set of Cahn-Hilliard and Allen-Cahn equations, the model captures several relevant processes including vacancy annihilation and nucleation at grain boundaries (GBs), vacancy diffusion toward sinks (including GBs and void surfaces) as well as void nucleation and growth due to vacancy supersaturations occurring in the grain interiors. Illustrative results are presented that characterize the rate of annihilation of the vacancy population at the GB sinks, as well as the formation of void denuded zones adjacent to GBs in bicrystalline and polycrystalline samples, the width of which is found to depend on both the vacancy diffusivity and the vacancy production rate.