基于复合中间层设计的镁铝异质金属高能束胶焊冶金连接机制研究

The research is mainly about the controlling of hard and brittle and continuous intermetallic formed in the Mg and Al dissimilar welding joint, which makes obviously harmful influence on the static and dynamic performance of the joint. In the application, the hybrid interlayer composed of adhesive and third-party alloying elements is introduced into the high energy beam weld bonding of Mg to Al dissimilar joint, in order to eliminate the adverse effects of intermetallics, and significantly improve the fundamental purpose of the joining performance. Through studing the effect of hybrid interlayer composed of adhesive and third-party alloying elements on the Mg and Al welding metallurgy reaction, reveals the controlling mechnicam of hybrid interlayer layer on the intermetallic compounds in the molten pool. Through the analyzing the influence of micostructure and defect evolution on the fatigue property of the high energy beam weld bonding Mg to Al joint, put forward the accordance enhancement mechanism of welding joint and adhesive bonding joint and reveals the relationship of microstructure defect and dynamic mechanical properties in high energy beam weld bonding joint。In the project, the welding metallurgy reaction in Mg and Al dissimilar joint will be regulated precisely by the design of hybrid interlayer, and establish the microstructure evolution and mechanical properties evaluation model in high energy beam weld bonding Mg to Al dissimilar joint. It would explore the new approach of joining Mg and Al alloys, and provide technical support to resolve the analogous problems in dissimilar metals joining process.

本申请针对镁/铝异质金属焊接过程中，形成硬脆且连续分布的金属间化合物，显著影响镁/铝异质连接接头动静态性能的核心问题，通过将第三方合金元素及有机胶粘剂组成复合中间层引入到镁/铝异质金属高能束胶焊过程之中，达到消除金属间化合物不良影响，显著提高接头性能的根本目的。本项目通过研究胶粘剂与第三方合金元素组成的复合中间层对镁铝异质金属焊接冶金反应的影响规律，揭示复合中间层控制熔池中金属间化合物的作用机制；研究不同复合中间层作用下高能束胶焊焊接接头组织对整体构件动态性能的影响机制，建立焊接接头与胶接接头有机增强匹配的边界条件，揭示高能束胶焊接头组织缺陷及动态力学性能间的关联作用规律。本项目通过复合中间层设计实现对镁铝异质轻合金焊接冶金反应过程的精确调控，建立镁/铝异质轻合金高能束胶接焊接头组织结构演变及力学性能评价模型，探索镁/铝异质轻合金结构连接的新方法，为解决类似的异质金属连接问题提供技术支撑。

本项目针对镁-铝异种金属焊接易形成金属间化合物，显著影响焊接接头性能的核心问题。采用激光胶焊技术，通过胶粘剂和金属中间层的复合作用实现了镁-铝异种金属的良好连接。分析了复合中间层对金属间化合物的影响，阐明了胶粘剂失效对焊接接头力学性能的影响机制，提出了基于激光电弧复合胶焊的轻合金与钢的连接方法，对于实现异种金属的高性能连接提供了有效的技术支撑。按照项目计划完成了全部的研究内容，具体如下。.1）基于金属与胶粘剂复合中间层的组合模式及其影响规律.分别讨论Cu、Ni及Fe等不同金属中间层对焊接接头性能的影响机制，通过胶粘剂与中间层的复合作用有效减少或消除了Mg-Al金属间化合物对焊接接头的不良影响，进而显著提高了镁-铝异种金属焊接接头的整体性能。其中金属中间层主要通过改变元素之间的反应过程来调控金属间化合物种类，胶粘剂主要通过改变焊接过程中的传热和传质过程来影响焊接接头内部组织和元素分布。.2）胶粘剂分解逸出对焊接接头组织及性能的影响机制.研究了在激光作用下焊接热影响区位置胶粘剂的分解失效现象，发现随着激光能量增大胶粘剂失效面积先增大后保持不变，胶粘剂单侧失效面积小于0.75mm时对整体结构的力学性能影响不明显，当胶粘剂单侧失效面积超过2.0mm以上，对焊接接头拉伸及疲劳性能带来显著不良影响。金属中间层与胶粘剂组成复合中间层后，因金属中间层能够阻挡热影响区的激光能量，能够有效改善了激光焊接热影响区的胶粘剂失效问题，在一定程度上拓宽了激光胶焊技术的焊接工艺区间。.3）基于激光-电弧复合胶焊的轻合金与钢的异种金属连接方法.在采用激光胶焊技术实现镁-铝异种金属高性能连接的基础上，将该技术向轻合金与钢铁材料连接拓展，通过采用激光-电弧复合胶焊技术，实现了镁-钢及钛-钢的之间的良好连接，为进一步开展轻合金与黑色金属的异种材料连接奠定了良好基础。