It was recalled that superplasticity in fine-grained materials was generally analyzed on the basis of experimental strain rate-flow stress relationships. Such phenomenological analysis, based upon a constitutive equation, was effective for understanding the overall flow and fracture behaviour and for speculating on the rate-controlling mechanism of superplastic flow. However, it had been pointed out that high-temperature superplastic flow and failure in ceramics was significantly influenced by the atomic structure and chemistry of grain boundary. This could not be explained on the basis of classical phenomenological analysis. It was therefore proposed to establish a new research field (grain boundary plasticity), in order to describe superplastic deformation which was related to the grain boundary quantum structure.

High Temperature Grain Boundary Plasticity in Ceramics. T.Sakuma, H.Yoshida: Materials Transactions, 2009, 50[2], 229-35