Microstructural evolution of Al2O3–SiC nanocomposites during spark plasma sintering

Al2O3–SiC nanocomposites were fabricated using a spark plasma sintering (SPS) technique, and their densification behavior and mechanical properties were investigated. The rate of densification was higher for the SPS process compared with a conventional hot-pressing process. This enhancement was attributed to an acceleration of the diffusion process due to additional mass-transport mechanisms induced by the spark plasma. Al2O3–SiC nanocomposites were found to possess microstructures of fine SiC particles dispersed within the Al2O3 matrix grains and/or at the grain boundaries. These nanocomposites (20 vol% SiC) had an average fracture toughness of 3.6 MPa m1/2 and flexural strength of 812 MPa compared with 2.95 MPa m1/2 and 663 MPa for the pure Al2O3 compacts, respectively. These increases over the pure matrix have been attributed to the increased rate of densification and to the change in microstructure due to the dispersion of the nano-sized second phase SiC particles.