A novel rapid route for in situ synthesizing TiB-TiB₂ composites

The in situ synthesized TiB-TiB₂ ceramic-matrix composite is prepared by spark plasma sintering using Ti and TiB₂ powders. The microstructures, mechanical properties and the sintering mechanism of the composites are investigated. The composite sintered at 1700 °C has a relative density of 99.4%, average Vickers hardness of 26.5 GPa, flexural strength of 661 MPa and fracture toughness of 6.95 MPa m^1/2. According to the microstructure evolution of the composites, the description of the sintering process can be divided into four stages: activation and melt of the metal powder, reaction of Ti with TiB₂, coarsening of TiB, and rapid densification. Only if the above mentioned sintering stages proceed in turn and are all fully completed, the high quality composite can be obtained.