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 mum, and Ti3SiC2 is about 2-10 mum 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 deg C-1 for Ti3SiC2-40 vol.%TiC composite.