Fabrication and Properties of TiC/SiC Whisker Composites

TiC/SiC whisker composites were fabricated by the hot-press method. As a sintering additive, 10wt% Cr7C3 was added and dense sintered bodies were obtained by 1600°C-1h hot-pressing. Mechanical properties of the sintered bodies were influenced by the grain size and the dispersion of the sintering additive. For a grain size of Cr7C3 of 3.53μm, flexural strength (σf) and KIC had maximum values of 660MPa (Vf=10%, hot-pressed at 1600°C for 1h) and 5.2MPa√m(Vf=30%, hot-pressed at 1750°C for 1h), respectively. On the other hand, when hot-pressed at 1900°C for 1.5h without any sintering additive, σf and KIC were 690MPa and 6MPa√m at Vf of 10%, respectively. In the 1900°C-sintered specimens the whiskers and surrounding matrix were ripped off together from the fractured surface, indicating that the crack bowing and deflection have occurred. Such behaviour was not found in the specimens containing a sintering additive, and their whiskers were fractured at the same plane as the matrix fracture surface. This is the reason that 1900°C-1.5h hot-pressed specimens without sintering additive had higher KIC than that with sintering additive. The different fractured surfaces are probably dependent on the residual thermal stress conditions caused by the difference in hot-pressing temperature or by the presence of Cr7C3 in the matrix/whisker interface.