Effect of AlN–Y2O3 addition on the properties and microstructure of in-situ strengthened SiC–TiB2 composites prepared by hot pressing

SiC–TiB2 composites with 20 vol% TiB2 were fabricated by in situ reaction among TiO2, C and B4C. Samples were densified by hot-pressing at 1900 °C with AlN and Y2O3 as sintering aids. The effects of the volume fraction of AlN and Y2O3 on the density, flexural strength, hardness and microstructure of the SiC–TiB2 composites were determined. The results showed that SiC–TiB2 composites possess the best comprehensive performance when the content of sintering aids is 10 vol%, at which point the relative density, flexural strength and hardness of the sintered specimens were 99.1%, 641±45 MPa and 91.8±0.7 HRA, respectively. The resistivity of the SiC–TiB2 composites decreased with increasing AlN–Y2O3 content and reached a minimum (17.5±6.7 mΩ cm) at 10 vol% AlN–Y2O3. Pull-out of crystal particles in the sintered body with 10 vol% AlN–Y2O3 was observed from the fracture morphology of the composites. Tightly bonded grains contributed to the excellent combination of properties of SiC–TiB2 composites.