Effect of starting SiC particle size on in situ fabrication of Ti5Si3/TiC composites

Spark plasma sintering (SPS) was used to in situ fabricate Ti5Si3/TiC composites using SiC and Ti powders as starting materials. The microstructure characterization of the composites was performed by means of XRD, SEM and TEM. The influence of the starting SiC particle size on resulted composites has been investigated. When nano-SiC and submicro-SiC powder were used, the reaction products mainly consisted of Ti5Si3 and TiC phase without other phases. While micro-SiC was used, the resulted product contained TiC, Ti3SiC2 Ti5Si3, and free SiC phase. All the samples exhibited similar microstructure which TiC grains are very fine (grain size less than 200 nm). While a small fraction Ti3SiC2 grains (∼1 μm) and unreacted SiC grains (∼10 μm) were found in the composites using micro-SiC as starting powder. The fracture toughness of composites at room temperature was determined by means of indentation test. The results showed that the fracture toughness of all the composites exceeded of monolithic Ti5Si3 and the maximum value of 5.1 ± 0.3 MPa m1/2 was obtained in Ti5Si3/TiC composites using micro-SiC starting powder.