Effect of TiC content on the microstructure and properties of Ti₃SiC₂-TiC composites in situ fabricated by spark plasma sintering

Spark plasma sintering technique was used to in situ fabricate high dense Ti₃SiC₂-TiC composites. The calculated TiC volume content from X-ray diffraction (XRD) is close to the theoretical one. It is found from fracture surface observation that TiC is about 1 μm, and Ti₃SiC₂ is about 2-10 μm in grain size. The fracture modes consist of intergranular mainly for Ti₃SiC₂ and transgranular fracture mainly for TiC. With the increasing of TiC volume content, Vickers hardness increases to the maximum value of 13 GPa for Ti₃SiC₂-40 vol.%TiC. Fracture toughness and flexural strength of the composites are also improved compared with those of monolithic Ti₃SiC₂ except for Ti₃SiC₂-40 vol.%TiC composite. The main reasons for the sudden decrease of fracture toughness and flexural strength of Ti₃SiC₂-40 vol.%TiC composite can be attributed to the relatively lower density, some clusters of TiC in the composite and the transition of fracture mode from intergranular to transgranular. The thermal conductivities decreased with the addition of TiC. The minimum thermal conductivity is 22 W m °C^-1 for Ti₃SiC₂-40 vol.%TiC composite.