INVESTIGATION OF MICROSTUCTURAL AND MECHANICAL PROPERTIES OF FRICTION STIR WELDED Cu/Al-1050 BUTT JOINT

In this study, the weldability of pure copper (Cu) plate to aluminum (Al-1050) plate has been investigated at a constant tool rotation speed of 515 rpm and different weld speeds by friction stir welding. While a relatively sound Cu/Al-1050 joint was achieved at the lowest weld speed (12 mm min(-1)), very poor joints were obtained at the higher weld speeds (30 and 50 mm min(-1)). Therefore in this study, microstructural characterization and mechanical properties of the joint at weld speed of 12 mm min(-1) were evaluated. Microstructure investigations by optical microscope and scanning electron microscope, energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), tensile test and microhardness measurements were carried out in this joint. Microstructure inspections and EDS analysis revealed that the stir zone of the joint consisted of aluminum-rich and copper-rich structures. AlCu, Al2Cu3, AlCu4 and Al4Cu9 intermetallic compounds were detected in the weld region by XRD. Volume fraction of copper-rich phases in the stir zone was calculated by image analysis software which is approximately 32%. Tensile test results show that the tensile strength of Cu/Al-1050 joint lower 50% and 24% 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 the base metals and varied between 74 HV and 280 HV.