Effect of micro-alumina content on mechanical properties of Al2O3/3Y-TZP composites

3 mol% yttria-stabilized zirconia (3Y-TZP) ceramic composites containing 0 to 50 vol% of micro-alumina were prepared. The effect and mechanism of micro-alumina addition on their mechanical properties were investigated in this paper. The results show that with less than 20 vol% micro-alumina, hardness and relative density vary slightly and flexural strength increases dramatically. For micro-alumina content over 20 vol%, hardness and relative density reduce severely and flexural strength varies slightly. Compared with 3Y-TZP ceramic, the hardness and relative density of the composite with 50 vol% micro-alumina decrease by about 29.4% and 5.8%, respectively, but the flexural strength of the composite with 20 vol% micro-alumina increases by similar to 15.8%. With increasing micro-alumina content from 0 to 50 vol%, the fracture toughness of the composite increases by approximately 32.7%, and the fracture mode of the 3Y-TZP grains changes gradually from intergranular to transgranular. While the transgranular fracture of 3Y-TZP grains is mostly found around micro-alumina particles. The strengthening is mainly attributed to the dispersion strengthening effect of micro-alumina particles. The increase in fracture toughness should be due not only to the crack deflection by dispersed micro-alumina particles and the increase in transgranular fracture of the composites, but also by the phase transformation of t-ZrO2 accelerated by the residual stress from the coefficient of thermal expansion (CTE) mismatch between 3Y-TZP and alumina. For micro-alumina content over 10 vol%, the increase in fracture toughness is mainly attributed to the transformation toughening of t-ZrO2. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.