ZrO2-Al2O3 composites with tailored toughness

The goal of this present contribution is to show how to tailor the toughness of ZrO2-Al2O3 composites based on tuning the ZrO2 matrix composition when all sintered under identical conditions. Commercial co-precipitated ZrO2 starting powders as well as a range of experimental ZrO2 powder mixture grades, obtained by mixing of 3 mol% Y2O3 co-precipitated ZrO2 with Y-free monoclinic ZrO2, were used for the fabrication of yttria-stabilised tetragonal zirconia (Y-TZP) composites with 20 wt.% (28 vol.%) Al2O3 by means of hot pressing in vacuum at 1450degreesC for 1 h. The microstructure and mechanical properties are also compared with the commercial ZrO2-20 wt.% Al2O3 ceramic. The observed difference in obtained toughness is explained in terms of the yttria content, the yttria distribution, and the residual stress due to the presence of the Al2O3 particles. Transformation toughening is observed to be the major toughening mechanism. The inhomogeneous Y-distribution and reduced overall yttria content, established by the "mixing route", is found to result in an increased toughness of the newly developed composites up to similar to10MPam(1/2), which is just double than the commercial ZrO2-20 wt.% Al2O3 ceramic. Based on our research results, a simple route to tailor the toughness of the TZP-Al2O3 composites is proposed. (C) 2003 Elsevier B.V. All rights reserved.