Properties and micro-structure of ZrO2–Al2O3 composites with three-layer structure

For obtaining a high toughness accompanied with an increasing strength, ZrO2–Al2O3 composites with a three-layer structure were fabricated. Special residual stress occurred after sintering by means of calculated compositions for toughening along with a special pressing process. And the interface of composites and crystallology’s characteristics were observed and analyzed. Both of the toughness and the strength of the composites are greater than those of the monolayer ones. L30 with 30 wt%Al2O3 + ZrO2 in surface layer and 5 wt%Al2O3 + ZrO2 in center layer is the best one on properties of the whole series of laminated composites: the fracture strength is 786 MPa and the fracture toughness is 18.37 MPa m1/2. The designed residual stress not only led to much more toughness for the composites, but also gave rise to some changes including the restricted tetragonal grain growth and a tiny movement of the orientation relations between t- and m- phases after phase transformation.