Hybrid Ti matrix composites with TiB2 and TiC compounds

Abstract

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 TiBw 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 TiBw 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 TiC1-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.