Effect of ultrasonic energy on the spot weldability of aluminum alloy AA6061
Effect of ultrasonic energy on the spot weldability of aluminum alloy AA6061
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DOI：
10.1016/j.matdes.2020.108690
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发表时间：
2020-07
影响因子：
8.4
通讯作者：
U. Shah;Xun Liu
中科院分区：
文献类型：
--
作者：
U. Shah;Xun Liu
研究了叠加超声振动对AA6061-T6铝合金电阻点焊的影响。采用一种新的超声辅助电阻点焊工艺--超声电阻焊(URW)，在不同条件下对AA6061进行了焊接，并与RSW焊接结果进行了比较。URW焊缝的搭接剪切拉伸试验表明，与RSW焊缝相比，URW焊缝的力学性能显著改善，包括更高的强度、更好的延性和更高的破坏前吸收的能量。焊缝断面的光学显微镜观察表明，超声振动促进了熔核的形成，减少了气孔缺陷。此外，URW焊缝的熔核中心普遍存在等轴晶组织，而RSW熔合区以柱状晶为主。这两个过程的原位热成像显示，在URW过程中，温度分布较低，加热和降温速率较小。这归因于超声波辅助的表面氧化物和污染物的断裂和击穿，从而降低了接触电阻和产热率。
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.