Influence of Nanoparticle Addition (TiO2) on Microstructural Evolution and Mechanical Properties of Friction Stir Welded AA6061-T6 Joints

Attempts were made in the present study to evaluate the effect of titanium oxide nanoparticles addition on microstructural evolution and mechanical properties of friction stir welded 6061-T6 aluminum alloy joints. Optical microscopy and scanning electron microscopy was utilized to evaluate the microstructures of the produced joints (nanocomposites) and to ascertain the distribution of titanium oxide nano-range particles in the processed zone. Results reveal that the produced nanocomposites have a uniform distribution of titanium oxide nanoparticles across the perpendicular x-section of a welded processed zone via Zener-pinning effect occurred due to the presence of titanium oxide nanoparticles that helps to prevent the coarsening of grains accompanied by recrystallization throughout the friction stir welding process, resulted in significant grain size reduction. With the increase in volume percentage of titanium oxide nanoparticles, a remarkable increase in the microhardness was noticed. It was also noticed that the ultimate tensile strength and the resistance to wear of produced nanocomposite can be significantly increased with the addition of titanium oxide nanoparticles as compared to parent metal joints. The corresponding mechanical properties’ results were correlated with microstructure and fractography.