A possible flow mechanism of zirconia in alumina-zirconia composites superplastically deformed in compression

The aim of this study is to investigate the possibility that zirconia particles deform plastically during superplastic compression of alumina-zirconia composites. Various plastic deformation mechanisms of zirconia (dislocation activity, lattice and grain boundary diffusion) are taken into account in a self-consistent model which predicts the mechanical behaviour of a composite when the viscoplastic laws of each phase are known. The predicted results are compared with the experimental data, i.e. the macroscopic rheology of the composites and the physical parameters related to the deformation of zirconia. From the comparison between the model and the experiments, a possible mechanism of plastic deformation of zirconia is proposed. (C) 1997 Acta Metallurgica Inc.