采用Zn-Al钎料超声辅助钎焊连接了钛合金与铝合金, 利用OM, SEM, EDS和TEM分析了钎焊接头的微观组织. 利用数字图像相关(DIC)方法分析了Ti/Al钎焊接头在原位拉伸过程中应变变化及裂纹扩展情况. 结果表明, 在钛合金/钎缝界面上有2种化合物, 分别为Ti₇Al₅Si₁₂和TiAl₃, 而在铝合金/钎缝界面上存在一层Zn-Al扩散层, 钎缝组织由富Zn相和Zn-Al共析组织构成. 原位拉伸过程中, 钎焊接头整体应变较低, 局部高应变区呈条纹状形态分布, 接头没有发生明显屈服过程, 只有弹性变形和塑性变形阶段. 在应变相对较大的富Zn相内部产生最大应力且出现裂纹, 裂纹曲析扩展最后呈锯齿状断裂.

The prospect of joining titanium and aluminum components into structures is desirable for a wide range of aerospace and automobile industry applications. One of the problems related with the joining processes for dissimilar metals such as Ti and Al is the formation of residual stress in the bonded joint, which has significant effect on the joint mechanical properties. In this work, joining of a titanium alloy to an aluminum alloy by ultrasonic assisted brazing using a Zn-Al filler metal was investigated. The microstructures of the titanium/aluminum brazed joints were determined by OM, SEM and TEM. The local tensile deformation characteristics of the brazed joints were also examined using the digital image correlation (DIC) methodology by mapping the local strain distribution during in situ tensile tests. The results showed that the Ti₇Al₅Si₁₂ phase and the TiAl₃ phase were formed at the titanium/brazing seam interface. The brazing seam was primarily composed of a Zn-rich phase and a Zn-24.14%Al (mass fraction) eutectoid structure. At the aluminum/brazing seam interface, no interfacial reaction layer was observed and the primary phase Zn-Al dendrites nucleated at the aluminum base metal and grew into the inside of the bonding region. A diffusion layer was formed in the aluminum base metal. It was found that the tensile deformation of the brazed joints was highly heterogeneous, which led to the deflection of the crack during propagating in the joint. The fracture initiated at the Zn-rich phases, where contained the highest stress concentration due to their low elastic modulus, and propagated in the Zn-rich phases or through the interface between Zn-rich phase and Zn-Al eutectoid structure.