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 ◦C to 130 J/m2, which is about 6.5 times larger than that of monolithic
alumina at room temperature. The WOF decreases sharply with an increase in temperature above 400 ◦C. The enhanced toughening 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 of 0.7 in the matrix, which was
essentially due to the maximized tensile internal stress on zirconia in the dual-phase matrix.
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