针对新能源车用Cu/Al焊接端子的功能特点, 以Ag为中间层开展铜铝激光熔钎搭接焊工艺研究。通过添加不同厚度的银镀层和银箔, 分析接头抗拉强度、电阻率、显微形貌和组织成分变化。结果表明, Ag中间层添加有利于改善焊缝成型和焊接质量, 接头抗拉强度和电阻率均随Ag中间层厚度的增加先减小后增大; 在添加厚度为20 μm银箔时, 抗拉强度提高了近1/3, 电阻率减小至8.6×10－8/Ω·m。这主要与Ag有效抑制铜铝液相熔合、控制二元脆硬相生成有关。在铜侧边界形成“啮齿状”Al-Al2Cu-Ag2Al三元共晶相, 熔化区以枝晶α-Al为主, 界面层化合物种类少、分布均匀, 内部拉应力产生的裂纹减小, 有利于提高接头强度和降低电阻率。

In view of the functional characteristics of Cu/Al welding terminals for new energy vehicles, the laser brazing of copper-aluminum lap welding process is carried out with Ag as the middle layer. Tensile strength, resistivity, microstructure and composition of joints are analyzed by adding different thickness of silver plating and foils. The results show that the addition of Ag middle layer is beneficial to improve the weld forming and welding quality. With the increase of Ag middle layer thickness, the tensile strength and resistivity of joints decrease first and then increase. When the added foil thickness is 20 μm, the tensile strength increases by nearly 1/3, and the resistivity decreases to 8.6×10－8/(Ω·m), which is mainly related with the effective inhibition of the liquid phase fusion of copper and aluminum by Ag and the control of the brittle-hard phase formation. Al-Al2Cu-Ag2Al is formed on the copper side boundary, and the melting zone is dominated by α-Al. There are few kinds of compounds in the interface layer with uniform distribution, and the cracks caused by internal tensile stress are reduced, which are beneficial to the joints strength improvement and the resistivity reduction.