Evaluation of Structure and Mechanical Properties of Zirconia Reinforced Aluminium Matrix Composites

The mechanical and wear properties and the related microstructure of metal matrix composites (MMC) based on Aluminium (Al6061) with varying particle reinforcements (5%, 10% and 15%) of Zirconia were investigated. Stir casting process comprised of melting Aluminium at 900 °C and adding the reinforcement for 5 to 10 min at 800 °C. The mechanical properties were examined by tensile loading test, impact test and Vickers hardness test at ambient temperature. The microstructure characteristics contributing to significant changes in strength and ductility and affecting the failure mechanisms during deformation were characterised by scanning electron microscopy and optical microscopy images. Composite microstructure depicted uniform deposition of the ceramic throughout the matrix with the elimination of breakage, porosities and shrinkage. The microstructure observation also showed the formation of Zirconia particles (ZrO₂) at the interface. The experimental results showed significant improvement in hardness due to the incorporation of ZrO₂. Enhanced wear resistance behaviour compared to that of base alloy was observed and it improved with the increase in the volume fraction of the reinforcement. The investigation also showed an increase in the fracture toughness of the composites as the increase in the volume fraction can be attributed to the unique fracture toughness value of Zirconia. The tensile and impact strength of Aluminium alloy was found to be slightly higher than the composites due to its ductility.