Microstructures and Toughening Mechanisms of Y2O3 Doped Al2O3/ZrO2 Eutectic Composite Ceramics Prepared by SHS Melt-Growth Process
By introducing ZrO2(4Y) powder of suitable content into the thermit and based on oxidation-reduction reaction of the thermit and liquid-liquid phase separation of ceramics/metal under gravity, Al2O3/ZrO2(4Y) composite ceramics have been prepared through melt-growth with eutectic reaction under high degree of undercooling from SHS process. It has been found that the ceramics were composed of major rod-shaped sapphires with 8.0~12.0 aspect ratios and minor plate-like α-Al2O3 grains, and within the sapphires t-ZrO2 nano-micron fibers were embedded. Flexural strength and fracture toughness were measured to be 1256MPa and 13.2MPa·m1/2. It was obtained that a number of low energy interfaces (the interface distance on nano-micron scale) between two Al2O3/ZrO2 (4Y) phases and the strong compressive residual stress in the sapphires made the sapphires reinforced, forcing the crack to propagate along the rod-shaped sapphires; meanwhile, crack-bridging and pull-out of the sapphires, crack - bridging and frictionally interlocked effects of plate-like α-Al2O3 grains in the wake of crack tip also rendered the crack stabilization to arise.
Yafang Han et al.
L. Zhang et al., "Microstructures and Toughening Mechanisms of Y2O3 Doped Al2O3/ZrO2 Eutectic Composite Ceramics Prepared by SHS Melt-Growth Process", Materials Science Forum, Vols. 546-549, pp. 1619-1622, 2007