Effects of nano-Al2O3 particle addition on grain structure evolution and mechanical behaviour of friction-stir-processed Al

The fabrication of nano-composites is quite challenging because the uniform dispersion of nano-sized reinforcements in metallic substrates is difficult to achieve using powder metallurgy or liquid processing methods. In the present study, Al-based nano-composites reinforced with Al2O3 particles have been successfully fabricated using friction stir processing. The effects nano-Al2O3 particle addition on the evolution of the grain structure and mechanical behaviour of a friction-stir-processed Al matrix were studied and discussed in detail. It was revealed that the pinning effect of Al2O3 particles retarded grain growth following recrystallisation during FSP and led to a more pronounced reduction in grain size. Significant increases in the microhardness and tensile strength relative to Al under the same conditions were obtained by adding Al2O3 particles. A microstructural examination suggested that the voids initiated from the Al/Al2O3 interfaces during testing of the tensile strength of the nano-composites.