The aluminum alloys 2017A-T451 in form of sheet, and AISi9Mg in form of casted plate were joint by using the conventional Friction Stir Welding (butt welding) method. The applied parameters of welding were in the range of 450 -710 rpm rate of rotation, 450 -1120 mm/min linear velocity. Three types of welding were curried out: the welding line was in the center (in relation to the edges of welded elements), shifted towards 2017A alloy (advancing side), and shifted towards AISi9Mg alloy (retreating side). Samples were investigated using light microscope, scanning electron microscope (SEM), tensile test and measurement of microhardness was also done. Application of many welding parameters was aimed at determine the field parameters allow to obtain good quality welds. The experiments showed that a wide range of parameters allows for welding without macroscopic defects in the face of a weld. While the weld quality is also acceptable in terms of the internal structure, was obtained only for one type of welding. In this case, a large linear velocity above 1 m/min turned out to be favorable not only for the quality of the weld but also it let achieve greater efficiency of the process. The study of macro and microstructure of the weld allowed establishing of each alloys location within a weld and the way of mixing the materials. Areas, which chemical composition resulted from mixing both welded alloys, have been identified in the layer close to the face of the weld. One can be observed the way of mixing creates only a separate volume of AISi9Mg alloy surrounded by 2017A alloy in the further distance from the face of the weld. Areas AISi9Mg alloy are arranged in a narrow bands on the advancing side. This alloy is also present in larger volume at the bottom of the weld, at the junction of the main directions of flow of material during welding. Moreover, the analysis of the structure of the weld indicates a small range of movement of the material between the face of the weld and the weld nugget placed where there is no significant mixing of the material. The study of mechanical properties showed a significant effect of plastic deformation to improve the AISi9Mg alloy properties. In the workplace pin tool alloy 2017A also has a higher hardness than the heat affected zone. The distribution of hardness in the layer closest the face of the weld located confirms earlier observations on the transport of material from the retreating side to advancing side of the weld. However, the characteristics of the hardness on the cross section weld do not indicate the potential place of rupture of extending sample. Place of rupture of the sample is determined by the structure of casted element and as a consequence of this, the samples rupture out of the weld or within the weld where the material in the state after casting is present. The SEM observations of fracture samples broken in static tensile test also showed that the AlSi9Mg alloy, after processing by the FSW tool, has larger plasticity and refinement of the microstructure components.
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