(哈尔滨工业大学 先进焊接与连接国家重点实验室，哈尔滨 150001)
摘 要: 为了改善2A14铝合金TIG焊接头的显微组织与力学性能，在TIG焊过程中，利用超声变幅杆对焊缝进行超声冲击，超声通过固体母材和焊缝传入熔池内，影响熔池的流动及凝固，从而达到细化焊接接头晶粒和提高接头力学性能的目的，利用激光测振仪对熔池表面的振动进行测量。结果表明：超声冲击使焊接接头的显微组织发生明显的变化，焊缝中心和熔合区的晶粒由柱状晶变为了等轴晶，晶粒尺寸减小，第二相尺寸变小且分布更加分散。超声冲击使接头抗拉强度提高，抗拉强度由246.18 MPa 提高到265.50 MPa，断后伸长率由5.33%增加到6.47%。超声冲击使熔池的流动性增强，导致熔池内温度更加均匀；温度梯度减小，有利于等轴晶的形成及晶粒的细化。
关键字: 铝合金；超声冲击；TIG焊接；熔池；显微组织；力学性能
（State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China）
Abstract:In order to improve the microstructures and mechanical properties of tungsten inert gas(TIG) welded joint of 2A14 aluminum alloy, ultrasonic horn periodically impacts the seam during TIG welding. The ultrasound propagates into the weld pool through the weld and base material, so that the ultrasonic energy can effectively influence the fluidity and crystallization of weld pool. Finally, the grain was refined and the mechanical properties were improved for welded joints. The results show that the microstructures are significantly improved after applying the ultrasonic impact. The grain is changed from the column grain to the equiaxed grain in the weld center and the fusion zone, and the grain size decreases in the weld center. Moreover, the distribution of the second phase becomes more uniform and the size becomes smaller after applying the ultrasonic impact. The ultrasonic impact during TIG welding can improve the tensile strength of welded joint and it is improved from 246.18 MPa to 265.50 MPa. The elongation is improved from 5.33% to 6.47%. The ultrasonic impact can improve the fluidity of weld pool, which results in an uniform temperature, so that the form of equiaxed grain and the grain refinement can be promoted.
Key words: aluminum alloy; ultrasonic impact; TIG welding; weld pool; microstructure; mechanical property
