CONTRIBUTION OF T-]M-PHASE TRANSFORMATION TO THE TOUGHENING OF ZTA

The toughness increment resulting from the stress-induced dilatational component of the t --> m transformation is calculated for a zirconia-toughened-alumina (ZTA) composition containing a high proportion of tetragonal zirconia precipitates and is shown to agree very well with the experimental value. The good agreement is made possible by allowing for the mismatch in the elastic constants between the zirconia particles and alumina matrix, and for the observed variation in the size of the transformable tetragonal particles with the height of the transformation zone. The actual variation is estimated from known experimental data.