Abstract
Densification of SiC powder with total amounts of 2, 4, 8 wt% Al-B-C additive was carried out by spark plasma sintering (SPS). The unique features of the process are the possibilities of a very fast heating rate and a short soaking time to obtain fully-dense materials. The heating rate and applied pressure were kept at 100 K·minute−1 and 40 MPa, while the sintering temperature and soaking time varied from 1,700-1,800 oC for 10-40 minutes, respectively. The SPS-sintered SiC at 1,800 oC with different amounts of Al-B-C reached near-theoretical density. The sintered SiC ceramics were predominantly composed of 6H polytype with 15R and 4H polytype as minor phases. The microstructure of SiC sintered up to 1,750 oC consisted of equiaxed grains. In contrast, the growth of large elongated SiC grains in small matrix grains was shown in sintered bodies at 1800 oC, and a plate-like grains interlocking microstructure had been developed by increasing the soaking time at 1800 oC. The grain growth rate decreases with increasing amounts of Al-B-C in SiC, however, the volume fraction and the aspect ratio of large elongated SiC grains in the sintered bodies increased