It was recalled that, as atoms migrated along void surfaces and grain boundaries - driven by thermodynamic forces - the grain-boundary void changed in shape and volume; a rounded void could become unstable, and collapse. Void instability was the result of a competition between the variation in the elastic energy stored in the stressed solid, the void surface and the grain-boundary energies. Here, the instability conditions and the equilibrium shape of a gas-filled grain-boundary void were determined, and an expression was then derived for the shrinkage rate as a function of void spacing, applied stress and internal pressure build-up by gas in the void.

The Three-Dimensional Analysis for Diffusive Shrinkage of a Grain-Boundary Void in Stressed Solid. H.Wang, Z.Li: Journal of Materials Science, 2004, 39[10], 3425-32