412 SiCウィスカー強化Al_2O_3/ZrO_22相マトリックス複合材料の高温下での高靱性化

抄録

A unique temperature dependence of toughening is observed in an alumina/zirconia dual-phase matrix composite reinforced with silicon carbide whiskers. The work-of-fracture (WOF) of the composite is maximized at 400℃ to be 130J/m^2 which is about 6.5 times larger than that of monolithic alumina at room temperature. The WOF decreases steeply with an increase in temperature above 400℃. The toughening enhanced at elevated temperatures is described by the stress-induced transformation toughening of tetragonal zirconia, which is affected by the internal thermal stress owing to thermoelastic mismatch between the matrix and the whiskers. The maximum WOF is not given only by the stress-induced transformation but also by the crack-face bridging of the whiskers. The WOF was optimized at a specific zirconia volume fraction in the matrix of 0.7, which was basically due to the maximized tensile internal stress on zirconia in the dual-phase matrix.