In Situ ZrB(2) Formation in B(4)C Ceramics and Its Strengthening Mechanism on Mechanical Properties

In order to reduce the sintering temperature and improve the mechanical properties of B(4)C ceramics, ZrB(2) was formed in situ using the SPS sintering method with ZrO(2) and B(4)C as raw materials. Thermodynamic calculations revealed that CO pressure affected the formation of ZrB(2) at temperatures from 814 °C to 1100 °C. The experimental results showed that the ZrB(2) grain size was <5 µm and that the grains were uniformly distributed within the B(4)C ceramics. With an increase in ZrO(2) content, the Vickers hardness and flexural strength of the B(4)C ceramics first increased and then decreased, while the fracture toughness continuously increased. When the content of ZrO(2) was 15 wt%, the Vickers hardness, fracture toughness and flexural strength of B(4)C ceramics were 35.5 ± 0.63 GPa, 3.6 ± 0.24 MPa·m(1/2) and 403 ± 10 MPa, respectively. These results suggest that ZrB(2) inhibits B(4)C grain growth, eliminates crack tip stress, and provides fine grain to strengthen and toughen B(4)C ceramics.