Microstructure and properties of alumina-silicon carbide nanocomposites fabricated by pressureless sintering and post hot-isostatic pressing

Al2O3/5%SiC nanocomposites were fabricated by pressureless sintering using MgO as a sintering aid and then post hot-isostatic pressed (HIP), which can subsequently break through the disadvantage of hot-pressing process. The MgO additive was able to promote the densification of the composites, but could not induce the grain growth of Al2O3 matrix due to the grain growth inhibition by nano-sized SiC particles. After HIP treatment, Al2O3/SiC nanocomposites achieved full densification and homogeneous distribution of nano-sized SiC particles. Moreover, the fracture morphology of HIP treated specimens was identical with that of the hot-pressed Al2O3/SiC nanocomposites showing complete transgranular fracture. Consequently, high fracture strength of 1 GPa was achieved for the Al2O3/5%SiC nanocomposites by pressureless sintering and post HIP process.