Effect of in situ VSi2 and SiC phases on the sintering behavior and the mechanical properties of HfB2-based composites

In situ HfB 2 –SiC–VSi 2 composite was fabricated by reactive pressureless sintering at the temperature of 2150 °C for 4 h under a vacuum atmosphere. In situ SiC and VSi 2 reinforcements were formed using VC and Si powders as starting materials according to the following reaction: VC + 3Si = SiC + VSi 2 . Microstructural studies and thermodynamic calculations revealed that in situ VSi 2 and SiC phases were mostly formed and homogeneously distributed in HfB 2 skeleton. The results showed that the density of in situ HfB 2 –SiC–VSi 2 composite was 98%. Besides, the mechanical properties of the composite were effectively enhanced by the formation of in situ second phases. The Vickers hardness and the fracture toughness of the composite reached 20.1 GPa and 5.8 MPa m −1/2 , respectively.