焊丝成分对6061-T6铝合金双脉冲MIG焊缝组织与性能的影响

Effect of welding wire compositions on microstructures and mechanical properties of double pulsed MIG welding joint of 6061-T6 aluminum alloy

用ER4043焊丝和ER5356焊丝对6061-T6薄板铝合金双脉冲MIG焊缝组织与性能进行研究。结果表明:用ER5356焊丝焊接时,6061-T6铝合金接头的屈服、抗拉强度及断后伸长率均高于以ER4043焊丝作为填充的焊接接头,前者的焊接系数为0.72,而后者仅为0.65;两者焊接接头的显微硬度均以焊缝为中心近似对称分布,最低值出现在接头热影响区中的淬火区,ER5356焊丝焊接时接头的硬度较ER4043焊丝高;以ER5356焊丝作为填充时,6061-T6铝合金的焊缝为细小的铸态组织,枝晶相对较细,而用ER4043焊丝焊接时,焊缝为粗大的铸态组织,且枝晶较发达,两者熔合区的近缝侧为柱状晶,靠近热影响区一侧为细小的等轴晶组织。与原始母材相比,热影响区的晶粒产生一定程度的粗化。两者淬火区的晶粒内虽然都产生少量的二次相,但以ER5356焊丝作为填充时淬火区中的二次相较细小,且呈弥散分布。

Mechanical properties and microstructures of welded joint of 6061-T6 thin sheets were investigated using ER4043 and ER5356 welding wires by the method of double pulsed MIG（DP- MIG）welding. The results show that the ultimate tensile strength,yield strength and elongation of the joint welded with ER5356 welding wire are higher than that with ER4043 welding wire,and the corresponding welding coefficient is 0.72 and 0.65,respectively. The micro-hardness of the two kinds of joints is approximately symmetric distribution around the center of welding,and the lowest value appears in the quenching zone of the heat affected zone（HAZ）. The micro-hardness of joint with ER5356 welding wire is higher than that with ER4043 welding wire. The welding zone with ER5356 welding wire is characterized by small dendritic structure,while larger dendritic structure is detected with ER4043 welding wire. For both welding wires,the columnar grains form in the fusion zone on one side of the welding seam as well as equiaxial crystal on the other side,and the grains of HAZ coarsen as compared with the base metal. The precipitates,although detected in the quenching zone with both welding wires,are finer and dispersed with ER5356 welding wire.