The effect of hardness and rotational speed tools on tensile strength and micro-hardness of dissimilar joints of aluminum 6061- T6 and aluminum 7075-T6 by friction stir spot welding

In this research, friction stir spot welding on aluminum plates 7075 and 6061 was performed. The purpose of this work is to investigate the impact of the tool's hardness and its rotational speed by changing the layout of the plates on the mechanical properties of the made welds. Two tools were made of H13 steel, with different hadness was used. The mechanical properties of the weld were studied for shear strength and microhardness. The results showed that when the 6061 aluminum plate is located on top of the layout, the shear tensile strengths are less than the 7075 aluminum plate. Also, with the increase in the speed of the tool, the shear force force values have undergone a downward trend. The microhardness of the heat treatment device is higher than the microhardness of the raw material. Also, with increasing speed of tool, the obtained microconstability has a rising trend. This is due to the increased frictional heat transferred by the very high speed of the tool, which increased the hardness of the boiling region. The optimum mode is achieved at a speed of 1000 rpm and in a position where aluminum 7075 was placed on top of the plates.