Superplasticity resulting from cooperative grain boundary sliding

A physical model of superplastic deformation based on the experimental evidence for the existence of cooperative grain boundary sliding (CGBS) is proposed. This approach shins the focus of attention to the analysis of CGBS bands formation conditions and to the evaluation of their amount necessary for superplastic flow. The model accurately reproduces the observed dependencies of the Bow stress on the strain rate, gives a new physical meaning to the superplasticity strain rate interval, and provides a basis for explanation of such phenomena as the high strain rate superplasticity and influence of a sample thickness on superplastic properties of materials. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.