Microstructures and Multi-Toughening of ZrO2 Nano-Micron Fibers Self-Toughening Al2O3 Ceramics from In Situ Growth in the Melts Produced by Combustion Synthesis

Al2O3/24%ZrO2 composite, which is mainly composed of lath-shaped and rod-shaped α-Al2O3 matrix containing ZrO2 nano-micron fibers, was obtained from in-situ growth in the melts produced by combustion synthesis. The results from XRD, SEM and EPMA showed that, besides the rod-shaped and lath-shaped α-Al2O3 grains, there are also t-ZrO2 or m-ZrO2 independent phases and Cr metallic particles at the boundaries of rod-shaped grains. The strength and toughness were measured to be 1186 MPa and 12.8MPa·m0.5 respectively. The procedure for toughening ceramics relies on coordinated action of multiple toughening mechanisms involving reinforcement-induced toughening by ZrO2 nano-micron fibers, deflection-induced toughening, stress-induced transformation toughening, crack-bridging toughening by lath-shaped α-Al2O3 grains as well as deformation-induced toughening by Cr metallic particles, and promises the occurrence of a sharp rising R-curved behavior.