Influence of Alpha Nanoalumina Reinforcement Content on the Microstructure, Mechanical and Corrosion Properties of Al6061-Al₂O₃ Composite

Sol–gel prepared nanoparticles of alpha alumina were mixed in their varying weight percentage (0.5, 1, 1.5, 2 and 2.5 wt.%) with Al-6061 powder for synthesizing of Al6061-Al₂O₃ nanocomposites using powder metallurgy route. After sintering at 610 °C, microstructural, mechanical and corrosion properties of the composite samples were evaluated to see the effect of nanoalumina reinforcement content on these properties. Microstructural examination of the composites indicated the uniform distribution of nanoparticles up to their 2 wt.% content. Above this amount, distribution of nanoparticle attained saturation level and their accumulation started in the grain boundary regions. It is found that by increasing the nanoparticles content, the hardness and strength first increase and then decrease when amount of nanoparticle exceeds 2 wt.%. Reinforcement of 0.5-1 wt.% nanoparticle content has shown excellent corrosion resistance of the synthesized composites in 3.5% NaCl solution. After 1 wt.% incorporation of nanoparticles, a gradual increase in corrosion rate with the increase in nanoparticle content was measured and corrosion becomes worse than that of the base alloy in the presence of 2.5 wt.% nanoparticle content. Solution heat treatment followed by ageing of the composite samples was found highly beneficial for the increase in hardness.