中厚板铝/铜异种金属双面搅拌摩擦接头微观组织与力学性能

Microstructure and Mechanical Properties of Double-side Friction Stir Welding Joint of Medium-thick Al/Cu Dissimilar Plate

采用双面搅拌摩擦焊实现了12 mm AA6061-T6铝合金与T2纯铜的焊接,研究工艺参数对接头微观组织与力学性能的影响。研究发现,当两面焊缝采用相同工艺参数时,由于焊接变形,两面的焊缝成形具有明显差异,难以同时兼顾双面焊缝成形以获得优异的接头性能。为了进一步提高接头性能,将第一道焊缝的转速和焊速分别固定为600 r/min和400 mm/min,对第二道焊缝的焊接参数进行了优化。一方面通过优化第二道焊缝的焊速,即将第二道焊缝的转速固定为600 r/min,焊速分别采用300 mm/min,200 mm/min和100 mm/min,无缺陷的焊接接头在焊速100 mm/min时取得;另一方面通过优化第二道焊缝的转速,即将第二道焊缝的焊速固定为400 mm/min,转速分别采用800 r/min和1000 r/min。结果表明当转速800 r/min时,接头横截面无缺陷且获得了最大抗拉强度达到151 MPa,此时接头无宏观孔洞缺陷、铝/铜界面处无微裂纹且界面处生成了相对较薄的金属间化合物层,接头拉伸断裂于铝/铜界面,断裂方式为韧-脆混合断裂。

12 mm medium-thick AA6061-T6 aluminium alloy and T2 pure copper was welded by double-sided stir friction welding,the influence of welding parameters on the microstructure and mechanical properties of the joint was investigated.It was found that there are significant differences in the weld formation between the first-pass and second-pass welds at both sides due to welding distortion even through the same welding parameters were used for those two welds at both sides,making it difficult to achieve excellent joint properties.In order to further improve the joint properties,the rotational speed and welding speed of the first-pass weld were fixed at 600 r/min and 400 mm/min respectively,while the welding parameters of the second-pass weld were investigated and optimized.On one hand,the rotational speed of the second-pass weld was fixed at 600 r/min while change the welding speed to 300 mm/min,200 mm/min and 100 mm/min,respectively.A defect-free joint is achieved at the welding speed of 100 mm/min for the second-pass weld.On the other hand,the welding speed of the second-pass weld was fixed at 400 mm/min while change the rotational speed to 800 r/min and 1000 r/min,respectively.The results showed that the defect-free joint with a maximum tensile strength of 151 MPa was obtained at the tool rotation speed of 800 r/min for the second-pass weld.This is because there isn’t any cavity defects and micro-cracks at the aluminium/copper interface,as well as the relatively thin intermetallic compound layer was formed at the Al/Cu interface under the optimized condition.The joint was fractured at the aluminium/copper interface and the fracture mode was classified as a ductile-brittle mixed fracture.