Effect of damage rate on the kinetics of void nucleation and growth by phase field modeling for materials under irradiations

The void formation and growth in materials under irradiations is studied by a modified Cahn-Hilliard equation coupled with the explicit nucleation algorithm. Through the numerical simulations, the stages of incubation, nucleation, growth and coalescence of the irradiation induced voids are clearly observed with a faster kinetics for stronger damage rate. There seems to exist a critical damage rate g˙vc at which the kinetics speeds up significantly. For smaller damage rates, very few voids can be nucleated. But the nucleated voids can grow rather large with its average radius growing as Rv∝t1/d. For stronger irradiations, much more voids could be nucleated, but they cannot grow very large before coarsening. The growth follows a much faster kinetics as Rv∝t2/d. The critical damage rate g˙vc should be determined by the competition of the rate of diffusion and the rate of vacancy production due to irradiations.