Stress redistribution and cavity nucleation near a diffusively growing grain boundary cavity

This article considers the growth of an isolated grain boundary cavity by diffusive flow of matter along the cavity surface and onto the grain boundary, while surrounding grains deform elastically. The analysis addresses the early life of the cavity. in which surface diffusion is rapid enough to maintain a near-equilibrium cavity shape with a uniform curvature. Although the stress normal to the grain boundary is largest at the cavity edge in the purely elastic case, diffusive flow shifts the stress peak to many radii away from the cavity. The magnitude of the stress peak is typically 5-25% greater than the remote stress normal to the grain boundary. The probability of a new cavity nucleating in the stress peak of an existing cavity is predicted to increase as the cube of the site distance from the cavity. Secondly, the stress concentration provided by the existing cavity, despite the small value, is predicted to increase the nucleation rate by several orders of magnitude. (C) 2000 Elsevier Science Ltd. All rights reserved.