Superplastic Deformation Mechanisms of Alumina Zirconia Two Phase Ceramics

Deformation behavior at high temperature has been investigated for fine-grained Al2O3-20%ZrO2 (3 mol%Y2O3 doped ZrO2) ceramics prepared with no additives in order to characterize the superplastic deformation mechanism. Large strains are obtained by compression tests in the temperature range from 1400 to 1600°C. Grain boundary sliding is clearly found to take place during the superplastic deformation. The strain rate dependence of the flow stress and the apparent activation energy are differ between the lower and higher strain rate regions. The deformation mechanisms contributing to the total strain in the lower strain rate region are grain boundary sliding, intragranular strain and grain boundary diffusion creep. The rate controlling mechanism in the lower strain rate region is interface-controlled diffusion creep. The deformation mechanisms in the higher strain rate region are grain boundary sliding, intragranular strain and grain boundary diffusion creep. Among them, the grain boundary diffusion creep is the rate controlling mechanism and has almost no contribution to the total strain.