Microstructure and mechanical properties of hot-pressed ZrB2–SiC–ZrO2f ceramics with different sintering temperatures

Effect of the hot-pressing temperature (1750–1950 °C) on the microstructure and mechanical properties of the hot-pressed ZrB2–SiC–ZrO2f ceramics was investigated in detail. It was indicated that when the hot-pressing temperature was above 1900 °C, ZrO2 fibers were instable in ZrB2–SiC matrix which would degenerate into particles and the grain size of ZrO2 particles was bigger than the upper critical grain size so that the phase transformation of tetragonal to monoclinic phase would occur spontaneously during cooling process. The optimal hot-pressing temperature for this material system should be 1850 °C to obtain high performance of the ZrB2–SiC–ZrO2f ceramics. The flexural strength and fracture toughness were enhanced to 1086 ± 79 MPa and 6.9 ± 0.4 MPa m1/2, respectively. The toughness mechanism was mainly attributed to densification, phase transformation toughening, crack deflection, fibers fracture, fibers pull-out and fibers debonding.