A new approach was used to produce Al–10%Al2O3 surface nanocomposite on Al2024 substrate. This novel approach involved air plasma spraying of Al–10%Al2O3 powder to produce Al–10%Al2O3 coating on substrate. The coated material was then subjected to friction stir processing (FSP) to distribute Al2O3 particles into the substrate. Microstructure and mechanical properties of samples were investigated by optical microscopy (OM), scanning electron microscopy (SEM), micro-hardness and wear measurements. As a result, it was found that the Al2O3 particles were distributed uniformly inside the substrate with an average penetration depth of about 600 μm. The surface nanocomposites produced in this way had excellent bonding with the substrate. The micro-hardness of the surface nanocomposite was 230 Hv, much higher than 90 Hv for Al2024 substrate. The surface nanocomposites also exhibited lower friction coefficient and wear rate. It was found that the addition of Al2O3 nanoparticles to the Al2024 matrix alloy affect the mechanism of wear.
Surface metal–matrix nanocomposite fabricated by a new approach utilizing atmosphere plasma spray and friction stir processing. The Al2O3 nanoparticles were almost homogenously distributed in nanocomposite surface layer without any evidence of structural defects. The average thickness of the surface nanocomposite layer formed by this method was 600 μm. The average hardness of the resulting surface nanocomposite increased to about 230 Hv which is much higher than that of unreinforced material at same condition. Addition of Al2O3 nanoparticles to the Al2024 matrix changed the wear mechanism; the wear of surface nanocomposite layer involves delamination and removal of layers from the surface, creating debris of soft metallic flakes. The wear properties of the Al2024 alloy were considerably improved by the addition of Al2O3 nanoparticles, and the wear resistance of material was much higher than that of the unreinforced Al2024 alloy.
Keywords: Friction stir processing; Surface nanocomposite; Al2024; Al2O3; Hardness; Wear