Pore and microstructure change induced by SiC whiskers and particles in porous TiB2–TiC–Ti3SiC2 composites

Abstract

TiB2–TiC–Ti3SiC2 porous composites were prepared through a plasma heating reaction using powder mixtures of Ti, B4C SiC whiskers (SiCw) and SiC particles (SiCp). The effects of the SiCw and SiCp content on pore structures, phase constituents, microstructure, and crystal morphology of TiC were studied. The results show that TiC, TiB, Ti3B4 phases are formed within the 5Ti+B4C system. With the addition of SiCw and SiCp, the TiB and Ti3B4 phases are reduced, sometimes even disappeared. Interestingly, the content of TiB2 and TiC increased, resulting in Ti3SiC2 and TiSi2 being formed. The porosity of composites increases notably with the addition of SiCw. However, with the increase of SiCp, the porosity of the composites first decreases, followed by an increase. After adding the specified amount of SiCw/SiCp, the compressive strength of composites are improved significantly. Additionally, the pore size of the composites are decreased significantly with the addition of SiCw/SiCp. During the plasma heating process, some Si atoms will diffuse into the TiC lattice, which in turn made the cubic TiC grains into hexagonal lamellar TiC or Ti3SiC2 grains.