铝/镀锌钢薄板异种金属CMT熔钎焊接头组织与力学性能

Microstructure and Mechanical Properties of CMT Welding-brazing Joint for Dissimilar Materials between Aluminums and Galvanized Steels

采用冷金属过渡方法对铝合金和镀锌钢板进行了熔钎焊连接,使用扫描电镜、能谱分析和拉伸试验分析了接头的截面形貌、组织特征、焊接缺陷及力学性能。试验结果表明,铝合金和镀锌钢能得到成形美观、性能良好的搭接接头。对焊缝金属的组织特征分析表明,焊接接头由熔化区、中心界面区、过渡界面区和富锌区组成,在焊缝金属和镀锌板的界面区形成厚度为3～4μm的金属间化合物层(主要成分为Fe3Al、FeAl2、Fe2Al5和FeAl3),富锌区由富铝的固溶体和残留的锌组成。在进行拉伸试验时,断裂发生在热影响区,接头强度为204MPa。

The dissimilar materials,aluminum alloys and galvanized steels were joined by CMT welding-brazing method.Analyzing the macro feature of cross-section,microstructure,the defects and mechanical properties of welding-brazing joints with SEM,EDAX,tension text,it is shown that the lap joints with better properties and better weld appearance are formed between the aluminum alloys and galvanized steels.From the microstructure and formation of weld metal,the cross-section of the joint can be divided into four zones： weld metal,middle interface,transitional interface and zinc-rich zone.There is a continuous and compact inter-metallic compound layers with a thickness of 3～4μm,which is formed in the brazing interface zone between the weld metal and the galvanized steel sheet.The main components of the layer are Fe3Al,FeAl2,Fe2Al5 and FeAl3,then,the zinc-rich zone is mainly composed of aluminum-rich solid solution and residue of Zn.Tensile strength tests show that the joint is fractured in the aluminum heat affect zone,and the joint strength with 204MPa is obtained.