عنوان مقاله [English]
In order to evaluate the possibility of the similar and dissimilar welding of 5019 and 7039 aluminum alloys, plates of 3 mm thick from this alloy were welded via Self-Reacting Friction Stir Welding (SRFSW) method. Floating bobbin tool was designed and manufactured from heat –treatable hot working steel to perform the welding process. The effect of various process variables such as the shoulders pinching gap, the tool transverse speed and the tool rotational speed were investigated to establish a defect-free joint. Following the visual inspection and X-ray radiography, it was found that a defect-free joint is obtained at the transverse speed of 22 mm/min and rotational speed of 1120 rpm. The results of tensile test, also, revealed that the joint efficiency of 5019-5019, 7039-7039 and 7039-5019 joints are 72, 76 and 91.5%, respectively. Accordingly, these amounts were more than the joint efficiency of the fusion welding, and comparable with/more than the joint efficiency of Conventional Friction Stir Welding (CFSW). Microscopic evaluation of the fracture surface of welded pieces indicated that the dominant fracture mechanism for similar joints is the soft fracture, while the one for non-similar fracture is the brittle fracture. Assessment of the cross-sectional hardness of the welded pieces near the upper and lower shoulders showed that the degree of hardness near the lower shoulder of the tool is always higher, which can be attributed to the lower temperature of the work piece in this area.