Investigation on mechanical properties of nano-Al2O3-reinforced aluminum matrix composites

In this study, 0.75, 1.5, 2.5, 3.5, and 5 vol.% of alumina nanoparticles were incorporated into the A356 aluminum alloy by a mechanical stirrer and then, cylindrical specimens were cast at 800°C and 900°C. A uniform distribution of reinforcement, grain refinement of aluminum matrix, and presence of the minimal porosity was observed by microstructural characterization of the composite samples. Characterization of mechanical properties revealed that the presence of nanoparticles significantly increased compressive and tensile flow stress at both casting temperatures. The highest compressive flow stress was obtained by 2.5 vol.% of Al2O3 nanoparticles. It is then observed that the flow stress decreases when Al2O3 concentration increased further to 5 vol.% irrespective of the amount of deformation and casting temperature. It was revealed that the presence of nano-Al2O3 reinforcement led to significant improvement in 0.2% yield strength and ultimate tensile stress while the ductility of the aluminum matrix is retained. Fractography examination showed relatively ductile fracture in tensile-fractured samples.