Microstructures and mechanical properties of Al/Al2O3 surface nano-composite layer produced by friction stir processing

In this study, a new processing technique, friction stir processing (FSP) was attempted to incorporate nano-sized Al2O3 into 6082 aluminum alloy to form particulate composite surface layer. Samples were subjected to various numbers of FSP passes from one to four, with and without Al2O3 powder. Microstrucrural observations were carried out by employing optical and scanning electron microscopy (SEM) of the cross sections both parallel and perpendicular to the tool traverse direction. Mechanical properties include microhardness and wear resistance, were evaluated in detail. The results show that the increasing in number of FSP passes causes a more uniform in distribution of nano-sized alumina particles. The microhardness of the surface improves by three times as compared to that of the as-received Al alloy. A significant improvement in wear resistance in the nano-composite surfaced Al is observed as compared to the as-received Al. (C) 2008 Elsevier B.V. All rights reserved.