超声波辅助钎焊镁铝异种金属接头微观组织研究

Study on microstructure of Ultrasonic-assisted brazing Mg/Al dissimilar metal joints

摘要:

铝合金和镁合金都具有密度小，比强度高等优点，在航天、航空等行业得到了广泛的应用。但这两种金属焊接时极易生成脆性的金属间化合物，使其很难获得性能优良的接头。在钎焊时，如何选择钎料避免有害金属间化合物的生成，是获得铝/镁异种金属优质接头的关键。为此本文选用了Sn基和Zn基两种钎料，在大气下采用超声波辅助钎焊技术进行了6063铝合金/AZ31B镁合金的焊接，通过OM、SEM以及EDS能谱对比分析了两种钎料钎焊接头组织。实验结果表明，采用Sn基钎料，钎焊接头不会生成Mg-Al脆性金属间化合物，钎缝中会溶解Al元素，Al元素以Al基固溶体相和Ag（Al）相形式存在于钎焊接头中，并且在超声波作用时间达到4.5s时，Al元素均匀分布在整个钎缝中。采用Zn基钎料，钎焊接头中有大量脆性Mg/Al金属间化合物生成，同时在钎缝组织晶界处有第二相低熔点Sn颗粒的弥散分布。

Abstract:

Al alloy and Mg alloy, which have advantages of low density and high specific strength, are widely applied in aerospace industry, yet easily generate brittle intermetallic compound during welding, thereby causing great difficulty in acquisition of joints with excellent performance. Therefore, during soldering, choose of soldering filler metal which can avoid generation of harmful intermetallic compound is key to acquisition of high grade Al/Mg dissimilar metal joint. In this work, Sn-based and Zn-based soldering filling metals are chosen, 6063 Al alloy and AZ31B Mg alloy are welded by ultrasonic-assisted soldering at atmosphere, and contrastive analysis is carried out to the two solder joint microstructures of soldering filler metals by OM, SEM and EDS spectrum. The results indicated that when Sn-based soldering filler metal is adopted, the joint cannot generate Mg-Al brittle intermetallic compound, Al elements which dissolve in soldering seams exist in the joint in form of Al-Sn-Zn and Ag (Al) phases, and when the ultrasonic action time reaches 4.5s, the Al elements are uniformly distributed in the whole soldering seam. When Zn-based soldering filler metal is adopted, large amount of brittle Mg/Al intermetallic compound generate in the joint, and second-phased low-melting-point Sn particles disperse at the grain boundary of the soldering seam.