对6 mm厚5052铝合金中厚板进行搅拌摩擦焊, 分析了搅拌头转速和焊接速度对接头宏观形貌、拉伸性能和硬度的影响, 并观察了拉伸断口形貌。结果表明: 当搅拌头转速为800~1 600 r·min-1及焊接速度为80~560 mm·min-1时均可以获得无缺陷和力学性能良好的接头; 搅拌头转速过低时, 易出现“隧道”型缺陷; 随搅拌头转速增大或焊接速度降低, 焊核区面积逐渐减小, “洋葱环”间距逐渐增大; 焊核区由细小的等轴晶粒组成, 平均晶粒尺寸约为5 μm, 约为母材的1/10; 焊接工艺参数对接头力学性能的影响不显著, 在工艺范围内其接头强度均可达到母材的90%以上, 显微硬度则达88%以上; 断口源于接头背面的原始焊接界面, 沿原始界面断裂, 终于接头返回侧, 呈典型的切断断口形貌。

The friction stir welding process for 5052 aluminium alloy plate with 6 mm thickness was carried out, and the effects of rotation rate of spindle and welding rate on the macrograph, tensile properties and hardness of the joint were studied, and the tensile fracture morphology was observed. The results show that the joint without defect and with excellent mechanical properties was obtained when the spindle rate was 800-1 600 r·min-1 and welding rate was 80-560 mm·min-1, respectively. But a tunnel type defect emerged acrossing the joint at low spindle rate. With the spindle rate increasing or welding rate decreasing, the area of weld nugget decreased and the distance between rings increased gradually. The weld nugget area was composed of fine equiaxed grains with average grain size of 5 μm, which was 1/10 of that for the base material. Futhermore, the process parameters had no significant influence on mechanical properties of the joint, and the tensile strength and microhardness of the joint were more than 90 % and 88% of those for the base material, respectively. The fracture was initiated from the back side and fractured along the original interface of the joint, and ended in the return side lastly, exhibited typical cut-off fracture morphology.