钢/铝异种金属激光-MIG复合焊接接头组织与性能研究

Microstructure and Properties of Laser Welded-MIG Steel/Aluminum Dissimilar Metal Composite Welding Joint

采用激光-MIG复合焊接的方法对Q960钢/6061铝异种金属进行了焊接,对比分析了添加Cu前后复合焊接接头的显微组织、物相组成和力学性能的变化,并对其断口形貌进行了观察。结果表明,添加Cu后焊接接头仍然保持着典型熔-钎焊特征,但是IZ(界面区)区域的界面层形态发生了明显改变,界面层厚度从加Cu前的16μm降低至加Cu后的6μm,界面层中的针状Fe_4Al_(13)相和舌状Fe_2Al_5相转变为细小絮状Al_(13)(Fe,Cu)4和舌状Al_5(Fe,Cu)2相,界面层中的显微裂纹消失;加Cu后钢/铝复合焊接接头的最高硬度仍然出现在界面层,但是最高硬度相对加Cu前有明显降低,这主要与界面层中形成了Al_(13)(Fe,Cu)4和Al_5(Fe,Cu)2金属间化合物有关;加Cu后焊接接头的抗拉强度和伸长率相较于加Cu前分别提高了110.5%和183.3%,而断裂位置都处于钢/铝界面区。

The laser-MIG composite welding was used to weld Q960 steel/6061 aluminum dissimilar metal,and the microstructure,phase composition and mechanical properties of the composite welded joint before and after adding Cu were analyzed comparatively,and the fracture morphology was observed.The results reveal that the weld joint remains the typical melt brazing characteristics after Cu addition,and the interface layer of the IZ region presents obvious change,where the thickness of the interface layer is decreased from 16μm before adding Cu to 6μm after adding Cu,and the needle like Fe4Al13 phase and the tongue Fe2Al5 phase in the interface layer are transformed into fine block Al13(Fe,Cu)4 and tongue Al5(Fe,Cu)2,and microcracks in the interface layer disappear.The maximum hardness of the steel/aluminum composite welded joint after adding Cu still occurrs in the interface layer,however the maximum hardness is reduced significantly,which is mainly related to the formation of Al13(Fe,Cu)4 and Al5(Fe,Cu)2 intermetallic compound in the interface layer.After adding Cu,the tensile strength and elongation of welded joints are increased by 110.5%and 183.3%,respectively,compared with those of ones before Cu addition,while the fracture locations are all located at the steel/aluminum interface region.