Fractography of Stir Casted Al-ZrO2 Composites

In this study, Al-ZrO2 composites were produced by Vortex method using ZrO2 powder with 1 micron average diameter as reinforce particles and Al-356 as the matrix metal. The melt composites were stirred for 13 minutes, then casted into a metallic mold. Different samples of 5, 10 and 15 volume percent of ZrO2 in different casting temperatures of 750, 850 and 950oC were produced. The latter 2 casting temperatures are not a common practice but were chosen to enhance fluidity. Effects of volume percent of ZrO2 particles and casting temperature on tensile strength, microstructure, and fracture surfaces of Al-ZrO2 composites have been investigated. The highest tensile strength was achieved in the specimen containing 15 vol. % ZrO2 produced at 750°C which shows an increase of 60% in comparison to the Al-356 non-reinforced alloy. Microscopic investigations of fracture surfaces revealed that fracture in a brittle manner with little or no necking happening. By increasing ZrO2 content and casting temperature, the composites fracture goes in a more severely brittle manner.