1.
B
4C-TiB
2 ceramics (TiB
2 ranging 5~70 vol%) with Mo-Co-WC as the sintering additive were prepared by spark plasma sintering. In comparison with B
4C-TiB
2 without additive, the enhanced densification was evident in the sintered specimen with Mo-Co-WC additive. Core-rim structured grain was observed around TiB
2 grains. The interface of the rim between TiB
2 and B
4C phases demonstrated different feature: the inner borderline of the rim exhibited a smooth feature, whereas a sharp curved grain boundary was observed between the rim and the B
4C grain. The formation mechanism is discussed: the epitaxial growth of (Ti,Mo,W)B
2 rim around the TiB
2 core may occur as a result of the solid solution and dissolution-precipitation between TiB
2 phase and the sintering additive. It was revealed that the fracture toughness increased as the content of TiB
2 content increased, alongside the decreased hardness. B
4C-30 vol% TiB
2 specimen demonstrated the optimal combination of mechanical properties, reaching Vickers hardness of 24.3 GPa and fracture toughness of 3.33 MPa·m
1/2.
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