EFFECTS OF ZIRCONIA ADDITIONS ON THE SUPERPLASTICITY OF ALUMINA-ZIRCONIA COMPOSITES

The superplastic properties in compression of alumina-zirconia composi tes (0-20 vol.% of zirconia) were investigated at constant strain rate , in air and at temperatures ranging from 1300 to 1400 degrees C. The as-sintered materials have identical grain sizes and significant amoun ts of residual porosity. In the strain range where no appreciable dens ification occurs, the influence of zirconia additions was determined. The compressive stresses of the zirconia-containing materials (composi tes) are higher than in the case of alumina for identical conditions o f deformation. This difference is interpreted in terms of intergranula r segregation of Zr4+ ions in the composites. For the composites, the compressive stresses are roughly independent of the zirconia content. This result may be attributed to comparable sliding capacities of alum ina/zirconia interfaces and alumina grain boundaries.