Research On Friction Stir Welding Process Of Aluminum Alloy And Copper Dissimilar Joint

The Al/Cu dissimilar joint has been widely used in many structures,for the reason,composite structure composed of aluminum and copper will contribute to weight and cost reduction and making full use of its advantages,as its excellent heat and electric conductivity,corrosion resistance,formability,etc.However,aluminum and copper have obvious dissimilarity in physical and chemical properties,it is difficult to get Al/Cu dissimilar joint by traditional welding process.Thus we need to find out the better welding process for the connection of aluminum and copper.In this paper,the experiment researches were focus on the friction stir welding?FSW?process by 1060 aluminum,6082 aluminum alloy and T2 copper alloy?2mm in thickness?.In order to get how the welding parameters have effect on the forming,microstructure and properties of FSW welded joints,the major experiments of microstructure,micro-hardness and XRD were used to analyze.The Al/Cu dissimilar butt and lab joints were formed well and there weren't defectives.The grains in nugget zone of 1060/T2 butt joints were obviously refined due to dynamic recrystallization,and in the copper/nugget region was formed an alternating lamellar structure.In the 6082/T2 lap joints there were self-locked macroscopic structures and several different interface“Interactive organization”structures.And these local organization structures are to improve the combine property of the dissimilar Al/Cu FSW lap welds.The grain at the nugget zone of Al/Cu joints were refined because the dynamic recrystallization that lead to the hardness value rised,while at the heat affected zone the grain increased because the heat effect and lead to the hardness decreased.The mechanical properties of Al/Cu butt joints were generally low,when the welding direction parallel the rolling direction the maximum tensile strength of joint was 141 MPa,reached 95%of1060 base metal.Compared with copper plate at the upper plate,the formability and the shear strength were better when the aluminum plate on the upper plate,the maximum shear strength was 3.341KN,and the maximum shear strength was 2.266KN when the copper plate on the upper plate.The fracture were mixed fracture mode of Al/Cu friction stir welded butt and lab joints.The results of XRD and EDS analysis showed that the thin,uniform and continuous Al₂Cu and Al₄Cu₉ layers were formed at the interface,and parallelled to the rolling direction,only Al₂Cu phase.6082/T2 friction stir lap welding test,when the copper plate as the upper plate,the joints appeared Al₂Cu along with decreasing of welding speed.However,when aluminum as upper plate,the joints without forming intermetallic.The brittle and hard intermetallic compounds reduced the joint properties.