镁/钛激光熔钎焊界面微观结构与元素热力学行为分析

镁/钛(Mg/Ti)异种金属既不反应也不互溶的特性制约着两者之间的冶金结合和可靠连接。为解决这一问题并拓宽Mg、Ti的应用，采用富铝镁基焊丝对Mg/Ti实施激光填丝搭接焊，实现了Mg/Ti之间的连接。在此基础上，利用扫描电镜对界面进行观察分析，并利用Miedema二元热力学模型和Toop三元热力学模型对调控元素Al在界面处的扩散及连接机理进行研究。结果表明，在焊丝中调控元素Al的参与下，Mg/Ti界面处形成超薄的反应层，元素线扫描结果显示Al在靠近Ti一侧界面处富集，实现了界面的冶金结合。热力学计算结果显示，在界面处Al-Ti化合物具有更大的析出驱动力，而且Al在富Ti一侧的化学势较低，且Al的界面偏聚导致Al的化学势进一步下降，表明Al的扩散方式为上坡扩散。

Abstract

The main obstacles of metallurgical bonding and reliable joining of Mg/Ti dissimilar joint are their nonreactive and immiscible characteristics. To overcome those problems and expand their application, laser lap joining of Mg/Ti with Al-rich Mg based wire is carried out. Mg/Ti interface is observed with scanning electron microscope, and the role of Al element in interfacial diffusion and bonding mechanism is investigated based on the result of calculation of Miedema binary and Toop ternary thermodynamic model. The results demonstrate that an ultra-thin reaction layer is observed at the Mg/Ti interface with the help of Al elements from filler. The element line scan results show that enrichment of Al element is evidenced at the interface, indicating metallurgical bonding of Mg and Ti. Thermodynamic calculation result reveals Al- Ti intermetallic compound has more driving force than other compounds, which indicates that it is the compound firstly precipitated from the liquid. In addition, Al chemical potential near the Ti side is lower than that at other places. Al segregation at the interface further causes the decrease of Al chemical potential, indicating the behavior of Al element from Mg fusion zone to the interface is uphill diffusion.

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檀财旺, 黄煜华, 陈波, 李俐群, 冯吉才. 镁/钛激光熔钎焊界面微观结构与元素热力学行为分析[J]. 中国激光, 2016, 43(3): 0303009. Tan Caiwang, Huang Yuhua, Chen Bo, Li Liqun, Feng Jicai. Microstructure and Thermodynamic Behavior of Laser Welded-Brazed Mg/Ti Dissimilar Joint[J]. Chinese Journal of Lasers, 2016, 43(3): 0303009.

镁/钛激光熔钎焊界面微观结构与元素热力学行为分析

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