Ti/Al异种金属微电阻点焊接头特征及性能研究

Characteristic and mechanical properties of the joints of Ti/Al dissimilar metal by micro resistance spot welding

摘要:

对0.2 mm厚的1060纯铝和TC4钛合金薄板进行了微电阻点焊试验,研究了焊接电流I、焊接时间T和电极压力F对接头力学性能的影响,采用扫描电子显微镜(SEM)和能谱仪(EDS)对点焊接头的连接特征及断裂行为进行了深入研究,采用微区射线衍射仪(micro-XRD)测定了焊点的物相组成。结果表明：在焊接电流为0.3 ~ 0.7 kA范围内,焊点的拉剪力随着焊接电流的增加先增加后趋于平稳,在焊接时间2~6 cyc范围内,焊接时间对焊点的拉剪力无显著影响,在电极压力为40~280 N范围内,随着电极压力增加焊点拉剪力先增加后降低；当I=0.7 kA、T=3 cyc、F=160 N时点焊接头的拉剪力最高为91 N,断裂发生在热影响区；1060/TC4异种金属微电阻点焊形成了共同的熔核,熔核与TC4之间界面较为平整,但是与1060的结合面呈凹凸不平,在熔核内部生成了AlTi₃、Al₂Ti和Al₃Ti金属间化合物,焊核与铝侧界面处生成了针状化合物Al₃Ti,对焊点的强度起到重要作用。

Abstract:

1060 pure aluminum and TC4 alloy sheets with a thickness of 0.2 mm were micro resistance spot welded successfully. The effects of the welding current, welding time and electrode force on mechanical properties of the joints were studied. The joining feature and fracture behavior of the joints were analyzed by using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Also, the phase compositions of the joints were measured by using micro-X-ray diffraction (micro-XRD). The result shows that: with increasing the welding current, the tensile shear load of the joints increases first and then is steady when the welding current is in the range of 0.3~0.7 kA. However, the welding time has no significant effect on the tensile shear load of the joints when the welding time changes in the range of 2~6 cyc. The tensile shear load of the joints presents an increased first and then decreased trend with increasing of the electrode force in the range of 40~280 N. When the welding current is 0.7 kA, the welding time is 3 cyc and the electrode force is 160 N, the maximum tensile shear load of the joints reaches to 91 N, and the fracture occurs in the heat affected zone. A complete nugget is formed, and the interface on the TC4 side is relatively flat while it is unsmooth on the 1060 side. Inside the nugget, lots of Al₃Ti, Al₂Ti and AlTi₃ compounds are generated. And some needle-like Al₃Ti compounds are found at the interface of the 1060, which plays an important role in the strength of the joints.