Fabrication of CNT-reinforced 6061 aluminium alloy surface composites by friction stir processing

The priority for transportation industries is to improve fuel efficiency by employing light composites. Carbon nanotubes (CNTs) have been incorporated into polymers and ceramics as reinforcing fibers, with recent studies focusing on fabrication of metal matrix composites. Integration of CNTs with light metal alloys, such as Al-6061, is expected to make strong but light composites. In this study, friction stir processing (FSP) is used to manufacture CNT-reinforced aluminium alloy surface composites, and their ultimate tensile strength, yield strength, and ductility are investigated. Their strength reached up to 178 MPa for the samples manufactured with 1500 rpm speed and 80 mm/min feed rate. Scanning electron microscopy was used to investigate their fracture surface morphology, and ductile failure was revealed. The highest temperature rise of 270°C was recorded during FSP, which is just above the plasticization temperature but far below the melting temperature of Al-6061 for the phase to change.