TC4/6061异种金属电阻点焊接头组织与性能研究

Research on microstructure and properties of TC4/6061 dissimilar metal resistance spot welding joint

采用2 mm厚的TC4钛合金和1.5 mm厚的6061铝合金进行电阻点焊,研究焊接热量与时间对接头拉剪力与熔核直径的影响,观察接头断裂特征并对接头进行了显微组织分析。试验结果表明:热影响区和熔核区的晶粒尺寸相对母材区变得粗大,靠近熔核的6061侧热影响区出现晶粒长大,TC4侧组织出现了细小的针状α'马氏体组织,并呈一定位向排列。随着焊接热量的增加,接头的拉剪力和焊核直径逐渐增加,随着焊接时间增加,接头的拉剪力和熔核直径先增加后减小;当Q=600 J时,接头的拉剪力最高,为1.17 kN。接头靠6061侧显微硬度无明显变化,靠TC4侧熔核区与热影响区硬度分布不均匀,当Q=550 J,t=10 s时硬度分布较理想。试验数据为钛/铝异种金属点焊提供理论指导。

Using 2 mm thick TC4 titanium alloy and 1.5 mm thick 6061 aluminum alloy as raw materials for resistance spot welding,the effects of heat and time on the tensile-shear force and nugget diameter of the joint were studied.The fracture characteristics of the joint were observed,and the microstructure of the joint was analyzed.The results show that the grain size of the heat affected zone and nugget zone become larger than the base material zone,the grain size of the heat affected zone for the 6061 aluminum alloy grows.The fineα'martensite structure of the TC4 side appears,and present directional distribution.With the increase of welding heat,the tensile shear and core diameter of the joint gradually increase.With the welding time prolonged,both of the tensile-shear force and core diameter of the joint increase first and then decrease.When Q=600 J,the highest tensile shear of the joint delivers is 1.17 kN.The microhardness of the 6061 aluminum alloy side of the joint has no obvious change,and the hardness distribution of the nugget zone and the heat affected zone of the TC4 alloy side is nonuniform.When Q=550 J and t=10 s,the ideal hardness distribution is obtained.These experimental data provide theoretical guidance for Ti/Al dissimilar metal spot welding.