Evaluating the Mechanical Features of Nano Alumina Reinforced Magnesium Alloy-fly Ash Nanocomposites

In this work, hybrid magnesium nanocomposite (HMNC) was fabricated with ultrasonic cavitation assisted bottom pouring stir casting method. For this, fixed quantity (7.5 wt.%) of fly ash (FA) and varying proportions of nano alumina (nAl2O3) (0, 0.5, 1, 1.5, and 2 wt.%) in AZ61 magnesium alloy matrix were used. Microstructural images reveal near homogeneous distribution of reinforcements with nAl2O3 available at the grain boundaries. The physical and mechanical properties were determined as per ASTM standards. It is found that the density and porosity tend to rise with increasing nAl2O3 content, whereas the porosity of 2 wt.% addition of nAl2O3 was very significant. The AZ61 alloy reinforced with 1.5 wt.% nAl2O3 and 7.5 wt.% FA exhibited enhanced strength and stiffness, which can be attributed to the Orowan strengthening mechanism and increased dislocation density. The 0.5 and 1 wt.% nAl2O3 reinforcement may be insufficient to effectively impede dislocation motion leading to limited improvements in mechanical properties. On the other hand, 2 wt.% nAl2O3 reinforcement leads to particle agglomeration and poor dispersion. This in turn, weakens the matrix-reinforcement interface and diminishes mechanical properties.