Hybrid Ti matrix composites with TiB₂ and TiC compounds

Spark plasma sintering method was utilized to produce monolithic Ti and four composite samples with different amount of TiB₂ and TiC as additives. The Sintering conditions of 1200 °C for 5 min under 50 MPa external pressure was employed for SPS process. The effect of different amount of additives was studied on the relative density, microstructure and mechanical characterizations of as-sintered samples. Microstructural investigations, thermodynamic assessments and XRD analysis revealed the formation of in-situ TiB_w phase in the Titanium matrix composites (TMCs). However, thanks to the short dwell time and existence of coarse TiB₂ particles, some semi reacted titanium diboride surrounded by TiB_w phase remained into the samples specially the ones with high TiB₂ contents. On the other hand, Titanium also diffuse into the TiC phase and the new phase of TiC_1-x was produced. The best relative density of 99.77 was obtained for monolithic sample. Adding additives decreased the UTS, elongation and bending strength of as-sintered samples whilst the hardness of specimens increased with addition of more TiB₂/TiC. The fractographs shown the role of additives on obtaining a finer microstructure by hindering the extensive grain growth. Predominant fracture mode was brittle and adding more additives rose up the transgranular fractures.