水下搅拌摩擦焊对铝/铜接头组织与性能的影响

目的 采用搅拌摩擦焊，对比分析大气环境和水下环境下铝/铜接头的组织与性能，以期获得力学性能更优异的铝/铜焊接接头。方法 利用搅拌摩擦焊，在焊接速度为40 mm/min、旋转速度为1 000 r/min的条件下，分别在大气环境和水下环境下对厚度为9 mm的6061铝合金板和T2纯铜板进行焊接。然后，对铝/铜界面、焊核区进行扫描电镜及能谱分析，并对铝/铜界面及焊核区进行物相分析，确定产物相组成。最后，对铝/铜试样进行拉伸及硬度检测。结果 铝/铜接头均无裂纹、气孔等缺陷。铜颗粒弥散分布在焊核区，铝/铜界面形成金属间化合物层。水下搅拌摩擦焊下界面元素扩散距离明显变短，且金属间化合物厚度更薄。铝/铜接头的金属间化合物为AlCu和Al4Cu9。大气环境焊接下接头的抗拉强度为130.6 MPa，断裂方式为脆性断裂;水下焊接下接头的抗拉强度为199.5 MPa，断裂方式为韧性断裂。水下环境下的接头硬度值更高，其中热影响区的硬度最低值约为65HV。结论 水下搅拌摩擦焊铝/铜接头无裂纹、气孔等缺陷。组织上，水下搅拌摩擦焊的铝/铜接头界面元素扩散距离更短，硬脆的金属间化合物更少;性能上，水下搅拌摩擦焊的铝/铜接头强度更高，抗拉强度达到199.5 MPa，达到母材的74.4%。

Effects of Underwater Friction Stir Welding on Microstructure and Properties of Al/Cu Joints

The work aims to use friction stir welding to compare and analyze the microstructure and properties of aluminum/copper joints in atmospheric environment and underwater environment, in order to obtain aluminum/copper welding joints of better mechanical properties. Using friction stir welding, 6061 aluminum alloy plates with thickness of 9 mm and T2 pure copper plates were welded at welding speed of 40 mm/min and rotation speed of 1 000 r/min in atmospheric environment and underwater environment respectively. Then, the Al/Cu interface and the nugget zone were analyzed by scanning electron microscope and energy spectrum, and the Al/Cu interface and the nugget zone were analyzed by phase analysis to determine the product composition. Finally, the tensile and hardness of Al/Cu samples were tested. Aluminum/copper joints were free of cracks, pores and other defects. The Cu particles were dispersed in the nugget zone, and the intermetallic compound layer was formed at the Al/Cu interface. The diffusion distance of interface elements was significantly shorter under underwater friction stir welding. Compared with friction stir welding, the thickness of intermetallic compound on the lower interface of underwater friction stir welding was thinner. The intermetallic compounds of Al/Cu joints were AlCu and Al4Cu9. The tensile strength of the joint welded in atmospheric environment was 130.6 MPa, and the fracture mode was brittle fracture. The tensile strength of the joint under underwater friction stir welding (UFSW) was 199.5 MPa, and the fracture mode was ductile fracture. The hardness value of joints in underwater environment was higher, and the minimum hardness value of heat affected zone was about 65HV. Underwater friction stir welding aluminum/copper joint has no cracks, pores and other defects. Microstructure shows shorter diffusion distance of elements at the interface of aluminum/copper joint and less hard and brittle intermetallic compounds. In terms of properties, the underwater friction stir welded aluminum/copper joint has higher strength, and the tensile strength reaches 199.5 MPa, which is 74.4% of the base metal.