Microstructure control and superplastic property of zirconia dispersed alumina ceramics

Superplasticity provides the possibility of high-temperature deformation processing of dense ceramics that has advantages of greater shape formability with better dimensional accuracy. To enhance the tensile ductility, microstructural design is required to get a fine grain size that is stable against coarsening during deformation at high-temperatures. Zirconia particle dispersed alumina is known to be effective in suppressing grain growth but the initial grain size of alumina reaches about 1μm using a conventional dry processing. In the present study, zirconia dispersed alumina composites were produced by colloidal process. Well-dispersed slurries consisting of α-Al₂O₃ and ZrO₂ fine powders were prepared by adjusting the pH value or adding appropriate amounts of polyelectrolyte. The slurries were consolidated by slip casting, followed by isostatic pressing (CIP). The consolidated bodies have small pore size and narrow pore size distribution, which enabled sintering at low-temperature of 1400°C and resulted in the desired fine-grained microstructure. It is demonstrated that large tensile elongation exceeding 550% can be obtained for the colloidally processed samples owing to dense, fine-grained and homogeneous microstructure.