| Aluminum and copper have been applied extensively in the fields like electric and electronics industries due to their good electrical and thermal conductivities.Al/Cu structures have been more and more used in light-weight applications.However,Al/Cu are difficult to be fusion welded because of their significant differences in physical and chemical properties.As a solid-state welding process,friction stir welding?FSW?has been a hotspot in Al/Cu joining.Recently,there still exists some problems such as poor appearance,lack of comprehensive properties evaluation.In this paper,2.5-mm-thick1060 aluminum and T2 pure copper were friction stir butt welded,and the formation mechanism of surface was clarified.The effect of parameters on the structure of joints and interface was clarified,and the comprehensive properties of joints were investigated.The effect of the parameters on joint appearance and the formation characteristics were investigated.It was shown the poor appearance was attributed to the adhering between the welding metal and FSW tool.The combined-shoulder tool could apply secondary forming on the joint surface to produce good appearance joint.The combination of low rotational speed,high welding speed and large offset could reduce the adhering.The formation of the adhering layer was due to the difference in shear yield strength between aluminum and copper,so washing the tool in copper at the end of welding is an effective method to produce long distance and high quality joint.The microstructure and macrostructure characteristics of Al/Cu joints as well as the effects of parameters were investigated.It demonstrated that nugget zone?WNZ?was composed of Cu particles or mixed lamellae in Al matrix.In mixed lamellae,the interdiffusion between Al Cu was more sufficient.Hole which deteriorates the properties may occur in the joint when the rotational speed is too low or the welding speed is too high.The effect of parameters on the interfacial characteristics were analyzed,and the evolution of the interface was clarified.It was shown intermetallic compounds?IMCs?layer would be thicker in the bending interface as rotational speed increases or welding speed decreases.The IMCs layer would be too thick when offset is too low,while kissing bond may exist in the bottom of interface when offset is too high.The thickness of IMCs layer needs to be controlled less than 2.5?m.The mechanical properties,conductive properties and corrosion behavior of Al/Cu joints in different parameters were evaluated,and the optimal parameters were obtained.It demonstrated that hole,kissing bond,microcrack and too thick IMCs layer could deteriorate the properties of joint.The optimized tensile strength of 90.73 MPa could be obtained at the rotational speed of 829 rpm,the welding speed of 562 mm/min and the offset of 0.83 mm.The joint obtained in the parameters could be 180°bending without failure,and the resistivity was 2.6431×10-8?·m.The corrosion behavior of Al/Cu joint was poor,and Nickel planting after welding could improve corrosion behavior effectively. |
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