الفهرس 
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Abstract
Aircraft structural elements are typically fabricated from high strength 2xxx and 7xxx series aluminium alloys. These alloys are often considered very difficult to weld using traditional welding techniques. This difficulty is one of the factors that have made riveting is the most popular joining technique for aircraft industry. Friction stir welding (FSW) technology is seen by engineering to be recommended as an alternative method for joining these materials. In the present study, two Al alloys ; AA2024 and AA7075 T-joints were successfully produced by FSW in two different combination ways of skins and stringers. For both configurations set up design ;T-lap (A-series) and T-butt (B series), the AA2024 and AA7075 Al alloys were chosen to be skin and stringer, respectively. Experiments were performed at at constant welding speed 50 mm/min and different rotational speeds of 400, 600 and 800 rpm. Two different tool geometry were used to weld The A and B series. The other FSW process parameters were kept constant. After FSW joint appearance, macrostructure and microstructure, and mechanical properties in terms of hardness and maximum load were investigated. The results showed that macro and micro analyses for A-series T-joints crosssections of the FSWed zones showed sound T-welds with no obvious defects at the top surface and left side. Whereas, a small corner defect in terms of tunnel was observed at right side at all the welding conditions. For B-series T-joint sound welds with no obvious macro and micro –defects were obtained at all the suggested welding parameters. In the current study, the hardness values, maximum failure load in both X and Y direction, and finally fracture mode of the joints are a function of the as received Al- alloys, type and design of joints, tool geometry, tool rotation speed at a constant travel speed of 50 mm/min.