Correlation between microstructural features, phase evolution and mechanical properties of TiB2-SiC composites

In densifying non-oxide high temperature ceramics like TiB2, the amount of sinter-aid critically determine the microstructural developments and consequently the mechanicalproperties. In this perspective, the present work is carried out to assess the feasibility whether SiC whiskers (SiCw) addition (up to 30 vol.%) can potentially improve the physical andmechanical properties (relative density, hardness and fracture toughness), while enhancing thedensification behaviour of TiB2. In order to answer such an important issue and to understand the mechanisms contributing to the variations in mechanical properties, TiB2–SiC ceramiccomposites with (15–30) vol. % SiCw were synthesized by the hot pressing process at 1850 °Cunder 20 MPa for 120 min in vacuum and the sintered specimens have been evaluated. For comparison, a monolithic TiB2 ceramic was also fabricated under the identical temperature,pressure, atmosphere, and holding time by the hot pressing process. The experimental results reveal that the addition of 20 vol. % SiCw to TiB2 results in the attainment of the highest relative density. Also, compared with the monolithic TiB2 ceramic, the hardness and fracturetoughness of TiB2–SiCw composites were greatly improved due to the presence of SiCw. The improved mechanical properties were attributed to the mixed fracture mode, the strengthening and toughening mechanisms of SiCw including crack bridging, crack deflection, crack branching and grain fracture.

Keywords:

TiB2 , SiCw , hot pressing , densification , hardness , toughening mechanisms