Superplastic Flow of Two‐Phase Ceramics Containing Rigid lnclusions— Zirconia/Mullite Composites

A continuum theory for non‐Newtonian flow of a two‐phase composite containing rigid inclusions is presented. It predicts flow suppression by a factor of (1 ‐ V) q , where V is the volume fraction of the rigid inclusion and q depends on the stress exponent and the inclusion shape. Stress concentrations in the rigid inclusion have also been evaluated. As the stress exponent increases, flow suppression is more pronounced even though stress concentration is less severe. To test this theory, superplastic flow of zirconia/mullite composites, in which zirconia is a soft, non‐Newtonian superplastic matrix and mullite is a rigid phase of various size, shape, and amount, is studied. The continuum theory is found to describe the two‐phase superplastic flow reasonably well.