Zirconia Particle Coarsening and the Effects of Zirconia Additions on the Mechanical Properties of Certain Commercial Aluminas

Abstract

The effects of ZrO 2 additions on the mechanical properties of four commercial aluminas have been studied, and the changes in intergranular and intragranular ZrO 2 particle sizes during aging have been determined for one of the aluminas. In this ceramic, the intercranular and intragranular ZrO 2 particles coarsen obeying t 1/2 and t 1/3 kinetics, respectively. Changes in strength of the aluminas with additions of ZrO 2 are shown to be related to changes in the Al 2 O 3 matrix microstructure. Differences in toughness of the resulting composites are explained in terms of the different size and morphology of the intergranular ZrO 2 particles and the operation of several toughening mechanisms, with transformation toughening a relatively minor contributor.