铝合金薄板搭接高速 FSW 缺陷及断裂行为

目的 为了拓展搅拌摩擦焊技术应用，对薄板搭接结构高速搅拌摩擦焊工艺优化与工程应用提供 借鉴与指导。方法 采用圆锥无螺纹搅拌针，进行了 6061 铝合金薄板搭接高速搅拌摩擦焊接，对接头界 面缺陷及其断裂模式进行分析，探讨了转速对 6061 铝合金薄板搭接接头成形及性能的影响规律。结果 发现在无螺纹圆锥搅拌针、高转速（6000~9000 r/min）条件下，接头塑性金属在后退侧易形成飞边流出， 导致下板前进侧出现孔洞缺陷，且随转速增大，界面缺陷尺寸逐渐增大，当转速达到 10 000 r/min 时， 孔洞尺寸有所减小，此时接头拉剪强度最高，为 123 MPa。对试样拉剪断裂位置分析发现，高速搭接接 头断裂位置主要有两种，分别断裂在结合界面处或在前进侧下板，且转速在 9000 r/min 以上越趋向于在 结合界面断裂。结论 高转速搭接焊接必须协调轴肩相貌、焊接工装约束等条件，保证接头塑性金属充 分流动而不流失，才能获得成形良好无缺陷的接头。

Defects of High Speed Friction Stir Welding and Fracture Behavior of Aluminum Alloy Thin Plate Lap Joints

The paper aims to expand the application of friction stir welding technology and provide reference and guidance for process optimization in engineering application of high-speed friction stir welding of thin plate lap joint structure. In this paper, the high-speed friction stir welding of 6061 aluminum alloy lap joints was carried out with conical screwless stirring pin. The joint interface defects and fracture modes were analyzed. And the influence of welding speed on the forming and performance of 6061 aluminum alloy thin plate lap joint was discussed. The results showed that the plastic metal of the lap joint weld nugget area was easy to form a flash edge on the retreating side under the condition of high speed (6000-9000 r/min), which lead to hole defects on the advancing side at lower plate. The size of the interface defects gradually increased with the increase of the rotational speed. When the rotational speed reached 10 000 r/min, the hole size decreased; and under this experimental conditions, the tensile strength of the joint was the highest, which was 123 MPa. The analysis of the tensile fracture position of the sample showed that there were two main types of tensile fracture at high speed lap joints, which were respectively broken at the joint interface or at the lower plate of the advanc- ing side; as the speed reached above 9000 r/min, the fracture position tended to be at the joint interface. The high-speed lap joint welding must coordinate the conditions of the tool shoulder and the welding tooling constraints to ensure that the plastic metal of the joint flows sufficiently without loss, so that a well-formed defect-free joint can be obtained.