SUPERPLASTICITY IN FINE-GRAINED CERAMICS AND CERAMIC COMPOSITES - CURRENT UNDERSTANDING AND FUTURE-PROSPECTS

Superplasticity in ceramics has now been reported in a wide range of materials with elongations to failure of more than 100%. Although the experimental observations of large deformation are in some ways similar to those reported in numerous metallic alloys, there are significant differences in the mechanical properties and cavitation failure characteristics of superplastic ceramics. This paper provides an overview of superplastic deformation and failure in ceramics, with specific emphasis on a 3 mol.% yttria stabilized zirconia and a zirconia-20wt.%alumina composite. It is demonstrated that there is a transition in the deformation behavior of zirconia which is dependent on the grain size and the impurity content of the material. Many of these materials fail by the nucleation, growth and interlinkage of cavities, so that the ductility is governed by the imposed stress and the grain size. Potential areas for additional research on superplastic ceramics are highlighted.