On the development of a nanocrystalline yttria stabilised zirconia ceramic capable of superplastic deformation at relatively low temperatures

Superplastic behaviour is well established in fine-grained zirconia ceramics at high temperatures (well above 0.5T_m, where T_m is the absolute melting point). In this study, an attempt was made to develop a nanocrystalline 5 mol.% yttria partially stabilised zirconia ceramic (5Y-PSZ) capable of exhibiting superplastic flow at relatively lower temperatures. A physical vapour processing route was used to synthesise the powders which was consolidated and subjected to a pressureless sintering route. Dense specimens with grain sizes in the nanometer range were subjected to tensile as well as compressive tests in the temperature range of 1283-1523K at different stress or strain rate levels in order to determine the superplastic deformation behaviour. The stress - strain - strain rate response of the material was analysed by a model for grain boundary sliding controlled superplastic flow. It was demonstrated that the strain rates predicted by the model are in close agreement with the experimentally observed ones.