Determination of the optimum welding parameters in joining Cu-Al plates by friction stir welding

Aluminum (Al) and copper (Cu) are two common engineering materials widely used in the aerospace, automotive, chemical, nuclear, electricity-electronics and energy industries. The joining of pure Cu and Al-1050 Al alloy, which possess different physical and chemical properties with the fusion welding methods leads to some difficulties, which particularly has negative effect on the mechanical properties of the weld. Therefore the joining of these different materials with friction stir welding (FSW), which is a solid state welding technique, is experimentally studied in this work. In this study, 1050 aluminum alloy and commercially pure copper sheets were welded at three different tool rotation speeds (525, 1025, 1525 rev/min), using three different tool travel speeds (50, 75, 100 mm/min) and two different pin positions (0.75, 1.5 mm) by FSW. Microstructure investigations by scanning electron microscope, X-ray diffraction (XRD), tensile test and microhardness measurements were carried out of these joints. Microstructural inspections revealed that the stir zone of the joint consisted of aluminum-rich and copper-rich structures. Al2Cu3, Al4Cu9 and Al0.0565Cu0.9434 intermetallic compounds were detected in the weld region by XRD. Tensile test results show that the best tensile strength of Cu/Al-1050 joint is 62% and 14% lower than that of Cu base metal and Al-1050 base metal, respectively. It was observed that hardness's in the stir zone increased when compared to that of base metals. Key Words: Friction stir welding (FSW), Cu/Al butt joint, mechanical properties, optimum welding parameters, aluminum alloy (Al-1050), commercial pure copper (Cu)