ZrO₂-toughened Al₂O₃ composites with better fracture and wear resistance properties

In view of the importance of the fracture resistance and wear properties on the performance and durability in a number of engineering applications, we have analysed such properties of sintered zirconia toughened alumina with varying zirconia content of 5 and 15 wt.%. Using micro-computed tomography, homogenous particulate distribution of zirconia is established through 3D volume rendering of the sintered pellet and by 2D orthoslice view. Depending on zirconia content and MgO addition (sintering additive), an interesting combination of strength and toughness properties was recorded with the investigated materials. While explaining the origin of cracking on worn surfaces of optimized zirconia toughened alumina, theoretical calculations revealed that the maximum tensile stress at the trailing edge of sliding contact is higher than critical damage stress. Such analysis incorporates the effect of factors such as the internal stresses due to thermal expansion anisotropy of non-cubic Al₂O₃ matrix, mismatch in elastic modulus/thermal expansion and athermal ZrO₂ phase transformation.