| Friction stir welding (FSW) is a solid-state joining process invented at The Welding Institute (TWI) in 1991.The ability to produce high-quality welds in high-strength aluminum alloys sets FSW apart from typical fusion welding techniques. The process has mainly been used for making butt joints in aluminum alloys. Development of FSW for use in overlap joint production would expand the number of applications that could benefit from the technique. For example, riveting of aerospace structures can be replaced by FSW overlap joints, aluminum alloy used in automobile industry can be joined by friction stir overlap welding rather than resistance spot welding (RSW), many possibilities are discussed to develop a viable FSW/SPF route for aluminum alloys similar to the DB/SPF technology for super plastic titanium alloys.Friction stir overlap welding has not been extensively used yet, in order to study this new technology, many studies has been carried out in this investigation. Five different tool pin profiles have been designed and used to weld LF21 aluminum alloy, the formation of FSP zone has been analyzed macroscopically, tensile properties of the joints has been evaluated and correlated with the FSP zone formation; Flared-TrifluteTM friction stir tool has been designed and fabricated and aluminum alloy 5083 has been friction stir overlap welded, it is revealed that the second weld pass can't affect the lowest hardness of the joint; 2-mm-thick LF21 aluminum alloy has been friction stir overlap welded with threaded cylindrical stir tool. The influence of thread on material flow path has been studied, it is found that the joint appear tunnel under inappropriate weld parameters; 2-mm-thick LF21 aluminum alloy has been friction stir lap welded with three different kinds of friction stir tools, a unique method has been designed to effectively survey the failure load of the overlap joint, sheet interface morphology has been surveyed, the failure position is located on the thinnest place. |
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