The influence of process parameters in friction stir welding of Al-Mg alloy and polycarbonate

The Role of rotating and travelling speed of the friction stir welding (FSW) tool on the dissimilar lap-joining of an AA5058 aluminum alloy and polycarbonate (PC) sheets has been investigated. The Relation of the processing parameters with tensile, bending strength, material flow and hardness of the joints were studied to attain defect-free joints with proper mechanical strength. The results showed both the size and the contribution of PC and aluminum alloy on the formation of stir zone are strongly related to the tool's rotational speed. Tool's rotational speed mainly controls the joint strength and the fracture mode, while traverse velocity affects the size of aluminum fragments within the PC matrix. The most suitable dissimilar lap-joining microstructure is achieved at 1600 rpm and 45 mm/min tool speed. Under this condition, the maximum joint tensile and bending strengths attained are 68.2% (46 MPa) and 69.4% (60 MPa) of PC raw material respectively. Fractography indicated that during the tensile test, the rupture occurs below and in the middle of the stir zone on AA5058 alloy/PC interface during the bending test. The hardness of the PC after FSW decreased by the molecular weight reduction and AA5058 micro-hardness increased because of the fine grinding after suffering thermo-mechanical cycle.