Effects of SiC whiskers on TiB₂-TiC porous composites by reaction synthesis

Porous TiB₂-TiC composites were produced by self-propagating high-temperature synthesis method, with Ti, B₄C and SiC whiskers(SiC_w) as raw materials. The effects of SiC_w content on phases, microstructures, porosity and compressive strength of TiB₂-TiC composites were studied. The results show that the composites are mainly composed of poor boron phases TiB and Ti₃B₄, TiC and a little TiB₂ when there is no SiC_w added. After adding SiC_w into 5Ti+B₄C system, the poor boron phases TiB and Ti₃B₄ decrease and even disappear, while the content of rich boron phase TiB₂ and TiC increase. With the increasing of SiC_w content, the porosity of composites gradually increases from 38.46% to 52.78%. When the content of SiC_w is less than 1.0, the compressive strength of porous TiB₂-TiC composites improves significantly with the increasing of SiC_w content and reaches to the maximum value of 56.04 MPa when the content of SiC_w is 1.0. A part of Ti is consumed by reacting with SiC_w to form TiC, Ti₃SiC₂ and TiSi₂ phases, so less Ti is remaining to react with B₄C. This promotes the formation of rich boron phase TiB₂ and TiC. Moreover some of the granular TiC or lamellar Ti₃SiC₂ grow around the surface of SiC_w, which is beneficial to improve the bonding strength of SiC_w and TiB₂-TiC matrix, and the effect of SiC_w reinforcement.