AZ61镁合金薄板TIG焊接头的组织和性能

Microstructure and Mechanical Properties of Welded Joint of AZ61 Magnesium Alloy Plates by TIG Welding

对3mm厚的AZ61镁合金薄板采用AZ31、AZ61两种焊丝进行TIG焊,探讨焊丝成分对焊接接头组织和性能的影响。通过光镜、扫描电镜、X-ray和力学性能测试等手段,分析了两种焊丝所焊接头的外观形貌、显微组织、焊缝析出相和力学性能等的差异。结果表明:采用这两种焊丝都能获得无明显缺陷的焊接接头,AZ61焊丝的焊缝宏观形貌优于AZ31。焊缝区组织为细小等轴晶,主要存在α-Mg和β-Mg17Al12两种相,热影响区组织较粗大。采用AZ31焊丝接头的焊缝区和热影响区硬度均低于母材;采用AZ61焊丝的接头与母材相比焊缝区硬度值较高而热影响区硬度较低。拉伸断裂位置均为热影响区粗晶区。

AZ61 plates with 3 mm thickness were welded by TIG welding with AZ31 and AZ61 welding wires,respectively.The influences of welding wires on the strength of the welded joints of AZ61 magnesium alloy plates were investigated.By OM,SEM,X-ray diffraction and etc.,the morphology,microstructure,deposited phase and mechanical properties were analyzed.The results show that the good appearance of the welded joint can be obtained with both AZ31 and AZ61 welding wires,the morphology of the welded joint with AZ61 welding wire is better than with AZ31 welding wire.The microstructure of the welded zone is fine equiaxed grain,which consists of α-Mg and β-Mg17Al12,and the microstructure of the heat affected zone is coarser.The microhardness of the weld zone and heat affected zone is lower than the base metal with AZ31 welding wire.With AZ61 welding wire,the microhardness of the weld zone is higher than base metal,while that of the heat affected zone is lower.The tensile fracture always occurs in the coarse grain of heat affected zone.