GRAIN-BOUNDARY SLIDING CONTRIBUTION TO SUPERPLASTIC DEFORMATION IN ALUMINA-ZIRCONIA COMPOSITES

Superplastic deformation in compression has been performed on Al2O3-Zr O2 laminated composites with volume fractions of zirconia from 0 to 20 %. In the as-sintered condition, the materials exhibit a fine-grained (0.2 mu m) microstructure, but show differences in residual porosity d epending on the zirconia content. The grain boundary sliding (GBS) con tribution is known to be the main mechanism of deformation in the supe rplastic regime. Its contribution to the total deformation can be obta ined from the knowledge of the intragranular deformation and from the strain due to densification. The contribution of the intragranular def ormation was estimated by two different methods, namely the measuremen t of the grain shape variation and the change in the crystallographic texture of alumina. The reliability of the two methods are discussed s ince some differences are observed. The higher GBS contribution in the materials which exhibit the lower residual porosity is also discussed .