A mesoscopic grain boundary sliding controlled flow model for superplasticity in intermetallics

Abstract

Abstract A model based on grain/interphase boundary sliding controlled flow that develops to a mesoscopic scale (defined to be equal to or more than a grain diameter) has been used to understand superplasticity in micrometer- and sub-micrometer grained intermetallics. The procedure for analyzing the experimental stress–strain rate data at a fixed initial grain size and temperature is so developed that the free energy of activation for the rate controlling deformation process, and the long range threshold stress which has to be overcome for boundary sliding to develop to a mesoscopic scale, σ0disloc, are estimated directly from the experimental results. The analysis is validated using experimental data pertaining to a number of systems. Directions for further development of the model are indicated.