Effects of sintering atmosphere on grain morphology of liquid-phase-sintered SiC with Al2O3 additions

The effects of sintering atmospheres of Ar and N2 on grain morphology were investigated for pressureless liquid-phase-sintered (LPS) SiC with Al2O3 additions. When increasing the sintering temperature, the SiC grain size and its aspect ratio increased in both sintering atmospheres. With a 2 mass% Al2O3 addition, no distinct difference was observed between the grain morphology of SiC sintered in the Ar atmosphere and that sintered in the N2 atmosphere. With a 15 mass% Al2O3 addition, sintering in a N2 atmosphere led to retarded grain growth and this resulted in a fine homogeneous microstructure, whereas sintering in an Ar atmosphere enhanced the grain growth compared with that in 2 mass% Al2O3. The effects of atmosphere on the grain morphology depend on the amount of Al2O3 addition, and this also affects the grain growth process of solution-reprecipitation. The mechanical properties of the SiC are also considered.