Microstructure and Mechanical Properties of Al2O3-SiC Nanocomposites with 0.05% MgO and Different SiC Volume Fraction

In this study, Al2O3-SiC nanocomposites have been fabricated by mixing of alumina powder containing 0.05% weight magnesium oxide and silicon carbide nano powders, followed by hot pressing at 16500C. The mechanical properties of Al2O3-SiC nanocomposites containing different volume fraction (2.5, 5, 7.5, 10 and 15%) of nano scale SiC particles were investigated and compared with those of alumina. The MgO additive was able to promote the densification of the nanocomposites. Al2O3-SiC powders were prepared by planetary milling in isopropanol. The fracture mode and microstructure of specimens was investigated by means of scanning electron microscopy. The nanocomposites were tougher compared to alumina when they were hot pressed at the same temperature. The young's modulus is decreased by increasing the volume percent of SiC. The values hardness and fracture toughness of the nanocomposites is increased by increasing the volume percent of SiC up to 7.5% and then decreased slightly. The ballistic energy dissipation ability is decreased by increasing the volume percent of SiC up to 5% and then increased slightly. The Scanning electron microscopy observations showed that fracture mode is changed from intergranular for alumina to transgranular for nanocomposites. It also shows the growth of grain is decreased by increasing the volume fraction of SiC particles. Finally X-ray diffraction analysis indicated that there was no chemical reaction between Al2O3 and SiC particles.