Cavitation

Abstract

AbstractCavitation is of great technical importance. Nucleated cavities grow and link to form cracks that can cause rupture. During creep, cavities are initiated in the grain boundaries. The nucleation takes place at particles or at subboundary—grain boundary junctions. The main mechanism is believed to be grain boundary sliding (GBS), Chap. 9. According to the double ledge model, cavities are formed when the particles or subboundaries meet other subboundaries. With this assumption quantitative models for cavity nucleation can be derived. They show that the nucleated number of cavities is proportional to the creep strain in good accordance with observations. Cavities can grow by diffusion or by straining. It is important to take into account that cavities cannot grow faster than the surrounding creeping matrix, which is referred to as constrained growth. Otherwise the growth rate can be significantly overestimated. Models both for diffusion and strain controlled growth have been available for a long time. A recently developed model for strain controlled growth is presented based on GBS. It has the advantage that is associated with a well-defined initiation size of cavities and that constrained growth is automatically taken into account, features that some previous strain controlled models miss.