Yong-Jai Kwon

Joining of 5083 and 6061 aluminum alloys by friction stir welding

Friction stir welding (FSW) has emerged as a new solid state joining technique [1], especially for aluminum alloys [2–6]. In this process, a rotating tool travels down the length of contacting metal plates, and produces a highly plastically deformed zone through the associated stirring action. The localized heating zone is produced by friction between the tool shoulder and the plate top surface, as well as plastic deformation of the material in contact with the tool [1]. At the present time, FSW is used mainly for joining similar materials. For dissimilar welding, there have been few systematic studies aimed at clarifying the effect of material combination and welding conditions on weld properties [7, 8]. However, FSW of dissimilar materials will be required in the near future for advanced aircraft design. In the present research, we have tried to apply the FSW technique to dissimilar light metals such as 5083 and 6061 aluminum alloys. Then, we have examined the microstructure and the mechanical properties of the FSWed aluminum alloy joint. 3 mm thick plates of cold-rolled 5083 (0.4%Si, 0.4%Fe, 0.4%Mn, 4%Mg, balance Al) and 6061T6 (0.7%Si, 0.7%Fe, 0.1%Mn, 1.0%Mg, 0.4%Cu, 0.1%Cr, balance Al) aluminum alloys were used in this experiment. Fig. 1 shows a schematic illustration of the experimental apparatus. The test piece was fixed onto a steel plate horizontally. Welding direction was perpendicular to the rolled direction of the aluminum plates. The diameter of the tool shoulder was 10 mm. The diameter of the insert pin and height were 3.0 mm and 2.8 mm respectively. The tool rotation speeds were 890 rpm and 1540 rpm. The traverse speeds of the moving table were 118 mm/min and 155 mm/min. Fig. 2 shows combinations of test pieces. Following FSW, microstructures of the samples were observed by optical microscopy. Vickers microhardness profiles

Mechanical properties of fine-grained aluminum alloy produced by friction stir process

The hardness and tensile strength of the friction stir-processed 1050 aluminum alloy increased significantly with decreased tool rotation speed. It is noteworthy that, at 560 rpm, these characteristics increased as a result of grain refinement by up to 37% and 46% respectively compared to the starting material.