Phase field crystal study on the grain boundary porosity induced by the Kirkendall effect

Abstract

Grain boundary (GB) porosity strongly degrades the bonding quality of interfaces and affects the physical and mechanical properties of solid polycrystalline materials. In this paper, the formation and evolution mechanisms of porosity at the grain boundary were investigated using the binary phase field crystal simulation method. Simulated results indicate that the Kirkendall effect existing in the interdiffusion of substitutional binary alloys can result in GB porosity. For the low-angle grain boundary interdiffusion system, the porosity initially forms at the isolated dislocation core, evolving from circle to irregular polygon. For the large-angle GB interdiffusion system, the porosity initially forms at the dislocation core close to the diffusion plane, and then evolves toward the dislocation cores away from the diffusion plane. The porosities finally connect as a continuous slit that splits up the GB. The results also show that the diffusion of fast diffusers along the GB is obviously enhanced with the mobility ratio of species A and B increasing. Our simulation results agree well with theoretical and experimental results.