辅助电流对Cu/Al大功率超声波焊接的影响

为获得更高质量的Cu/Al异质金属接头，开展了Cu/Al电流辅助大功率超声波焊接工艺试验，研究了辅助电流对Cu/Al超声波焊接的界面温度、材料塑性流动、界面中间相分布及接头力学性能的影响。结果表明，复合焊件成型良好，其接头抗拉剪力为3030 N，接头的断裂模式为韧性-脆性复合断裂。在同样的焊接时间0.2 s内，随着电流的增大，Cu/Al界面温度增加，金属塑性流动以及界面扩散也随之增强，这说明辅助电流能明显促进界面冶金；相比长时间0.4 s的超声波焊接，辅助电流能在保证界面温度、材料塑性变形的前提下，能明显减薄了界面IMC层的厚度，这是电流增强Cu/Al接头的主要物理机制。研究结果为优化Cu/Al复合焊接头强度提供了参考。

Effect of Assisted Current on High-Power Cu/Al Ultrasonic Welding

In order to obtain reliable Cu/Al dissimilar joints, current assisted Cu/Al high-power ultrasonic welding was proposed. The effects of current on the temperature rise, plastic flow, intermetallic compound (IMC) growth, and mechanical properties of the joints in Cu/Al ultrasonic welding were investigated. The results show that the obtained hybrid welded joint is well bonded, the tensile-shear force of the hybrid welding joint is 3030 N, and the fracture mode of the hybrid welding joint is ductile-brittle composite fracture. At the same welding time of 0.2 s, with the increase of the current, the peak temperature of the Cu/Al interface increases, and the metal plastic flow and diffusion at the interface also increase. This indicates that the assisted current can significantly enhance the interfacial metallurgy; compared with the single ultrasonic welding at welding time of 0.4 s, the assisted current can meet the welding formation requirements of interface temperature and material plastic deformation, but reduce the thickness of the interface IMC layer. This is the primary reason for the enhanced Cu/Al joint by assisted current. The results provide guidance for optimizing the strength of Cu/Al current assisted ultrasonic welded joints.