超声电弧对6061铝合金MIG焊接头组织和性能的影响

为了改善铝合金MIG焊的接头质量，利用外接超声激励装置在MIG焊接电弧中激发出超声，并研究了超声激励频率对6061铝合金对接焊缝的成形、气孔分布、显微组织及力学性能的影响规律. 结果表明，超声电弧可以有效的细化焊缝组织、减少焊缝气孔量，提升接头的强度. 与常规MIG焊接相比，在引入超声电弧后，焊缝的熔宽增加，焊缝中胞状树枝晶组织被细化，等轴晶区域占比增加，在激励频率为30 kHz时组织细化效果最好；随着激励频率的增加，焊缝中的气孔量逐渐降低，焊接接头的抗拉强度提高，当激励频率为50 kHz时，抗拉强度最高，达到235 MPa，为母材强度的73.4%，对应拉伸断口中韧窝的形态更加等轴化、分布更加均匀.

Effect of arc-ultrasonic on the microstructure and properties of 6061 aluminum alloy joint with MIG welding

To improve the quality of MIG welded joints of aluminum alloys, the ultrasonics were generated in the MIG welding arc with external ultrasonic excitation source, and the influence of the excitation frequency on the weld appearance, pore distribution, microstructure and mechanical properties of the 6061-T6 aluminum alloy butt weld was studied. The results show that arc-ultrasonic can effectively refine the microstructure of weld metal, reduce pores in the weld, and increase the strength of the welded joints. Compared with conventional MIG welding, arc-ultrasonic technique can increase the weld width, refine the cellular dendritic and enlarge the equiaxed grain zones in the weld metal. Microstructure refinement efficiency is most excellent when the excitation frequency is 30 kHz. As the excitation frequency increases, the number of pores in the weld gradually decreases, and the tensile strength of the joint is improved. The maximum tensile strength is 235 MPa, which is 73.4% of the base metal under the excitation frequency of 50 kHz, and accordingly the dimples in the tensile fracture have a more equiaxed shape and a more homogenized distribution.