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

Abstract SiC–TiB 2 composites with 20 vol% TiB 2 were fabricated by in situ reaction among TiO 2 , C and B 4 C. Samples were densified by hot-pressing at 1900 °C with AlN and Y 2 O 3 as sintering aids. The effects of the volume fraction of AlN and Y 2 O 3 on the density, flexural strength, hardness and microstructure of the SiC–TiB 2 composites were determined. The results showed that SiC–TiB 2 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–TiB 2 composites decreased with increasing AlN–Y 2 O 3 content and reached a minimum (17.5±6.7 mΩ cm) at 10 vol% AlN–Y 2 O 3 . Pull-out of crystal particles in the sintered body with 10 vol% AlN–Y 2 O 3 was observed from the fracture morphology of the composites. Tightly bonded grains contributed to the excellent combination of properties of SiC–TiB 2 composites.