Effects of zirconia additions on the superplasticity of alumina-zirconia composites

The superplastic properties in compression of alumina-zirconia composites (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 amounts of residual porosity. In the strain range where no appreciable densification occurs, the influence of zirconia additions was determined. The compressive stresses of the zirconia-containing materials (composites) are higher than in the case of alumina for identical conditions of deformation. This difference is interpreted in terms of intergranular 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 alumina/zirconia interfaces and alumina grain boundaries.