Influence of tool design and process parameters on dissimilar friction stir welding of copper to AA6061-T651 joints

In the present investigation, two different tool designs along with different process parameters such as tool pin offset, welding speed and axial plunge load were used to produce dissimilar copper to aluminium (6061-T651) friction stir welding joints. Macrostructure and microstructure analysis, tensile test, hardness measurement test, scattered electron microscopy and electron-dispersive tests were performed to evaluate the weldability and weld properties of dissimilar copper-aluminium joints. The results revealed that defect-free dissimilar friction stir welding was achieved using a cylindrical tool pin profile. On the other hand, the taper tool pin profile was not found to be suitable for dissimilar friction stir welding system (FSW). Maximum tensile strength of 133 MPa and hardness of 181 HV (in the nugget zone) were obtained when FSW process parameters such as rotational speed, welding speed, tilt angle, tool pin offset and tool pin profile were kept at 1500 rpm, 40 mm/min, 2A degrees, 2 mm and cylindrical profile, respectively. Axial plunge load value depended on the shoulder diameter as well as on the tilt angle. Axial plunge load range from 600 to 700 kgf was used to achieve defect-free copper to AA6061-T651 (of 6.3 mm in thickness) friction stir welded joint.