激光-粉末-胶层耦合调控的钢/镁熔化焊接机制研究

Magnesium alloy is applied in the field of modern transportation, known as the 21st century green engineering materials, it is inevitable for steel and magnesium connection.However,it is difficult realizing reliable welding for steel and magnesium due to the melting and boiling point difference, Mg and Fe almost no solution each other and no generating intermetallic compound.This project puts forward powder-adhesive layer aided laser welding technology, steel and magnesium are both melted by controlling heat transfer from steel to magnesium with the addition of adhesive layer.The metallurgy connection of steel/magnesium is realized based on the interaction or reaction generating new phase among the powder element with Fe and Mg.The diffusion of multicomponent composition in steel/magnesium interface and solidification process of molten pool are regulated by the use of coupled interaction among laser welding heat input, powder and adhesive layer in order to realize the stable coexistence of steel and magnesium liquid molten pool and accurate control of microstructure and composition of steel/magnesium interface.The design criterion of powder element will be explored, the change rules of temperature field distribution and dynamic behavior of the molten pool will be studied, and fusion welding mechanism of steel/magnesium will also be studied. Finally high mechanical property of steel/magnesium joint will be obtained based on the optimization of powder, adhesive layer and welding process parameters. Through the research, the project results will enrich steel/magnesium fusion welding technology forming theory, and provide new idea for the development of steel/magnesium structure parts application.

被誉为“21世纪绿色工程材料”的镁合金应用于现代交通运输领域，必涉及与钢的连接，但钢、镁熔沸点差异大，Mg在Fe中几乎不固溶，Mg与Fe之间不能形成金属间化合物，因此实现钢/镁可靠焊接十分困难。本项目提出粉末-胶层辅助激光焊技术，利用胶层调控钢/镁层间的热量传递，实现钢、镁同时熔化；利用粉末元素分别与Fe和Mg相互作用或反应生成新相，实现钢/镁冶金连接；利用激光焊接热输入、粉末和胶层的耦合作用，调控钢/镁界面多组元成分的扩散、反应及焊接熔池的凝固过程，实现钢、镁液态熔池的稳定共存及钢/镁界面组织和成分的精确控制。项目探索粉末元素设计准则，研究焊接接头温度场分布与熔池动态行为变化规律，以及钢/镁熔化焊接机制，通过粉末、胶层及焊接工艺参数的优化，获得高性能钢/镁焊接接头。本项目的研究成果将丰富和完善钢/镁熔化焊技术的成形理论，并为发展钢/镁结构件的推广应用提供新思路。

被誉为“21世纪绿色工程材料”的镁合金应用于现代交通运输领域，必涉及与钢的连接，但钢、镁熔沸点差异大，Mg在Fe中几乎不固溶，Mg与Fe之间不能形成金属间化合物，因此实现钢/镁可靠焊接十分困难。本项目探索了粉末-胶层辅助激光焊技术，通过粉末原子分别与Fe和Mg相互作用或反应生成新相的本征力学性质及对应体系电子结构的内在关联研究，明晰了添加元素的选择设计依据；研究焊接接头温度场分布及熔池动态行为变化规律，以及钢/镁熔化焊接机制，发现胶层起到隔热效果，有效调控了温度场，使镁侧温度不超过沸点而烧蚀汽化，利于钢/镁两者同时熔化和焊接熔池稳定，同时添加胶层增大熔池流动速度，促进钢/镁界面多组元成分的扩散、反应及焊接熔池的凝固过程；通过粉末、胶层及工艺参数对激光焊钢/镁焊缝形貌、焊接缺陷及接头性能影响规律，以及激光焊接热输入、粉末和胶层耦合作用对钢/镁界面显微组织和成分影响规律等研究，优化粉末、胶层以及焊接工艺参数，获得性能较好的钢/镁焊接接头。运用研究获得的成果为指导，拓展了不局限于钢/镁预制凹槽和添加粉末，以及塞铆-摆动激光焊等研究。通过本项目的研究，其成果丰富和完善钢/镁熔化焊技术的成形理论，并为发展钢/镁结构件的推广应用提供新思路。