Abstract Previous studies have shown that sharp physical and chemical changes may induce the formation of swirl-like reaction phases in the ultrasonic spot welding (USW) of different materials. However, the mechanisms have not been well understood. In particular, swirl-like structures have seldom been discovered or discussed in the USW of Cu/Sn. In this study, swirl-like phases were observed in the USW of a Sn-coated T2 Cu plate with different welding energies (300−400 J). The evolution of the microstructure from the flat region to the swirl region was studied, the diffusion coefficient of Cu in Sn and the peak temperature of the interface during welding were theoretically calculated and experimentally verified, the formation mechanism of the swirl-like phases was discussed, and the relationship between the joint properties and welding energies was investigated. The results show that the content of Cu3Sn increases, while that of Cu6Sn5 decreases gradually from the flat region to the swirl region and that grain refinement of Cu and IMCs occurs near the swirl regions. The greatly enhanced diffusivity shows that intense atomic diffusion takes place during the welding process. When the welding energy exceeds 300 J, the experimentally measured peak temperatures in the welding processes are higher than the theoretical values. The formation of the swirl-like phase is attributed to the uneven distribution of interfacial stress and the collapse of cavitation bubbles. When the welding energy reaches 400 J, the peak lap shear load of the welded specimen reaches 1008 N, and the associated fractures indicate the combined characteristics of ductility and brittleness.

中文翻译：

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涡旋状Cu-Sn相的形成及其对镀锡铜板超声波点焊接头的影响

摘要 以往的研究表明，在不同材料的超声点焊（USW）中，剧烈的物理和化学变化可能会导致漩涡状反应相的形成。然而，这些机制还没有被很好地理解。特别是，在 Cu/Sn 的 USW 中很少发现或讨论漩涡状结构。在这项研究中，在具有不同焊接能量 (300-400 J) 的 Sn 涂层 T2 Cu 板的 USW 中观察到漩涡状相。研究了组织从平坦区到旋涡区的演变过程，对Cu在Sn中的扩散系数和焊接时界面峰值温度进行了理论计算和实验验证，讨论了旋涡状相的形成机制。 , 并研究了接头性能与焊接能量之间的关系。结果表明，Cu3Sn的含量增加，而Cu6Sn5的含量从平坦区向涡旋区逐渐减少，并且在涡旋区附近发生Cu和IMCs的晶粒细化。大大增强的扩散率表明在焊接过程中发生了强烈的原子扩散。当焊接能量超过 300 J 时，焊接过程中实验测得的峰值温度高于理论值。漩涡状相的形成归因于界面应力的不均匀分布和空化气泡的坍塌。当焊接能量达到400 J时，焊接试样的搭接剪切载荷峰值达到1008 N，