The influence of grain size on cavitation in superplasticity

Superplasticity is observed in conventional metallic alloys, with a grain size of similar to 10 to 15 mu m, at a strain rate in the vicinity of similar to 10 s(-1). In order to enhance the commercial viability of this process, it is necessary to increase the optimum strain rate for superplasticity; one attractive means to achieving this objective is to reduce the grain size to the submicrometer and nanocrystalline ranges. Failure in many superplastic alloys occurs by the nucleation, growth and interlinkage of cavities. All of these processes may be influenced significantly by the grain size. This paper explores the influence of grain size on concurrent cavitation by developing a suitable theoretical framework and by examining some experimental data.