Abstract
Dense SiC–TiB 2 composites with 24 vol% TiB 2 were fabricated by pressureless sintering at 1940 °C. Al 2O 3 and Y 2O 3 were used as sintering additives to create a liquid phase and promote densification. TiB 2 was formed by an in situ reaction between TiO 2, B 4C and C. The sintered samples were subsequently heat-treated at temperatures ranging from 1850 °C to 2000 °C. The effect of temperature of post-sintering heat treatment on microstructure and mechanical properties of the SiC–TiB 2 composite was presented. Heat treatment at 1970 °C considerably improved the strength and the fracture toughness of sintered samples while maintaining high density. The elongation of α-SiC grains during the heat treatment was found to be responsible for an increase in fracture toughness. The presence of liquid phase assisted the elongation of grains which, in turn, activated crack bridging and crack deflection toughening mechanisms. Maximum strength of 540 MPa was found to be the result of improved fracture toughness. Heat treatment at temperatures above 1970 °C led to a deterioration of mechanical properties.
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