Abstract This study investigates the effects of superimposed ultrasonic vibration on resistance spot welding (RSW) of aluminum alloy AA6061-T6. A novel ultrasonically assisted resistance spot welding process, referred to as ultrasonic resistance welding (URW), is applied to weld AA6061 at various conditions and compared with the results from RSW. Lap shear tensile tests of URW welds show significantly improved mechanical properties, including higher strength, better ductility and higher amount of energy absorbed prior to failure compared with RSW welds. Optical micrographs of the weld cross section show that the ultrasonic vibration enhances nugget formation and minimizes porosities defects. Besides, equiaxed crystal structure is generally observed in the nugget center of URW welds whereas the majority of RSW fusion zone is dominated with columnar grain structure. In situ thermal imaging of the two processes shows a lower temperature distribution, smaller heating and cooling rates during URW. This is attributed to the ultrasonically assisted fracture and breakdown of surface oxides and contaminates, which reduces the contact resistance and accordingly heat generation rate.

中文翻译：

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超声波能量对AA60601铝合金点焊性的影响

摘要 本研究研究了叠加超声振动对AA6061-T6铝合金电阻点焊(RSW)的影响。一种新的超声波辅助电阻点焊工艺，称为超声波电阻焊 (URW)，适用于在各种条件下焊接 AA6061，并与 RSW 的结果进行比较。与 RSW 焊缝相比，URW 焊缝的搭接剪切拉伸试验显示出显着改善的机械性能，包括更高的强度、更好的延展性和更高的失效前吸收的能量。焊缝横截面的光学显微照片表明，超声波振动增强了熔核的形成并使气孔缺陷最小化。除了，在 URW 焊缝的熔核中心通常观察到等轴晶体结构，而大部分 RSW 熔合区以柱状晶粒结构为主。这两个过程的原位热成像显示 URW 期间温度分布较低，加热和冷却速率较小。这归因于表面氧化物和污染物的超声辅助断裂和分解，这降低了接触电阻并因此降低了发热率。