Abstract

The unique features of spark plasma sintering process are the possibilities of a very fast heating rate and a short holding time to obtain fully dense materials. beta-SiC powder with 0, 2, 6, 10 wt% of alpha-SiC particles (seeds) and 4 wt% of Al-B-C (sintering aids) were spark plasma sintered at 1700-1850°C for 10 min. The heating rate, applied pressure and sintering atmosphere were kept at 100°C/min, 40 MPa and a flowing Ar gas (500 CC/min). Microstructural development of SiC as function of seed content and temperature during spark plasma sintering was investigated quantitatively and statistically using image analysis. Quantitative image analyses on the sintered SiC ceramics were conducted on the grain size, aspect ratio and grain size distribution of SiC. The microstructure of SiC sintered up to 1700°C consisted of equiaxed grains. In contrast, the growth of large elongated SiC grains in small matrix grains was shown in sintered bodies at 1750°C and the plate-like grains interlocking microstructure had been developed by increasing sintering temperature. The introduction of alpha-SiC seeds into beta-SiC accelerated the grain growth of elongated grains during sintering, resulting in the plate-like grains interlocking microstructure. In the alpha-SiC seeds added in beta-SiC, the rate of grain growth decreased with alpha-SiC seed content, however, bulk density and aspect ratio of grains in sintered body increased.

• Keywords: SiC;Al-B-C additive;Liquid phase sintering;Spark plasma sintering;Microstructure;