为了解决传统铝合金焊接接头气孔数量多、晶粒粗大及力学性能差的问题,以5083-O铝合金为研究对象,进行了超声振动辅助激光-电弧复合焊接试验。研究了超声振动对铝合金焊缝气孔数量、微观组织及抗拉强度的影响,并探讨了超声波在焊接熔池中对气孔排出和组织细化的作用机理。结果表明,超声辅助焊接的焊缝气孔数量显著降低,主要归功于超声空化效应降低了铝合金熔体中的氢浓度,并促进气泡的快速逸出；超声波的空化效应和声流效应改变了熔体的压力、温度以及流动状态,使熔池的结晶条件发生改变,从而通过提高形核率和破碎枝晶细化了焊缝晶粒组织；施加超声振动后的焊缝平均拉伸强度由242.9MPa提高到270MPa,且断裂位置发生在热影响区,主要是因为焊缝区气孔减少和组织细化。此研究对深入理解铝合金焊接过程中缺陷形成机理及提高接头强度是有帮助的。

In order to solve the problems of large number of gas holes, coarse grain size and poor mechanical properties of traditional aluminum alloy welded joints, laser-arc hybrid welding experiment assisted by ultrasonic vibration was carried out by taking 5083-O aluminium alloy as the research object. The effect of ultrasonic vibration on the number of pore, microstructure and tensile strength of aluminium alloy weld was studied. The mechanism of the effect of ultrasonic wave on pore discharge and microstructure refinement in welding pool was also discussed. The results show that, the number of gas holes in the weld seam of ultrasonic assisted welding decreases significantly. It is mainly attributed to the reduction of hydrogen concentration in aluminium alloy melt by ultrasonic cavitation. It also promotes the rapid escape of bubbles. The cavitation effect and acoustic flow effect of ultrasound change the pressure, temperature and flow state of melt. The crystallization condition of the molten pool is changed. The grain structure of the weld is refined by increasing the nucleation rate and breaking dendrite. The average tensile strength of weld increased from 242.9MPa to 270MPa after ultrasonic vibration is applied. The fracture location occurs in the heat-affected zone. It is mainly due to the decrease of porosity and the refinement of structure in the weld zone. This study is helpful to understand the forming mechanism of defects and improve the strength of joints in the welding process of aluminium alloys.