Superplastic Deformation of Cubic Zirconia Ceramics with Intergranular Phases

Abstract

The effects of fine dispersions of alumina and amorphous silicate additions on high-temperature compressive deformation of 8 mol% cubic yttria stabilized zirconia (8Y-CSZ) was investigated. A fine grain size on the order of 1 μm was achieved with a dispersion of 10 wt% alumina in 8Y-CSZ while 0.5 μm grain size samples were produced by the addition of 5 wt.% colloidal silica. Strain rates in the rang of 10 -3 s - at were obtained for both sets of material, similar to the high strain rates observed for superplastic tetragonal yttria-stabilized zirconia. Over 130% true strain (260% nominal strain) could be obtained for the alumina-containing samples and over 180% true strain (505% nominal strain) could be obtained for the silica-containing samples. The stress exponent was around 2 for the alumina-containing samples and around 1.5 for the silica-containing smples. The activation energy for superplastic deformation was calculated to be in the range of 597-683 kJ/mol for the alumina-containing samples and 340-410 kJ/mol for the silica-containing samples. A discussion of models for optimal grain boundary engineering for superplasticity is included.