Cooperative grain-boundary sliding in polycrystalline ceramics

The microscopic processes and mechanisms are investigated for the superplastic deformation of 3mol% yttria-partially stabilized tetragonal zirconia polycrystals. Tensile tests are carried out by the use of test specimens with various dimensions in order to examine the specimen size effect on stress-strain curve. The formation and development of surface corrugation on tensile specimens induced during superplastic deformation are carefully studied as a function of tensile strain. New findings, i.e. the specimen size effect and the surface corrugation are discussed in terms of the concept of cooperative grain-boundary sliding as a candidate for superplastic deformation and flow of polycrystalline materials. (C) 2002 Elsevier Science Ltd. All rights reserved.