冷喷镍中间层铝/钢电阻点焊接头组织及力学性能

针对6061-T6铝合金和DP600双相钢的电阻点焊，焊前采用冷喷涂方法在铝合金母材待焊表面制备镍中间层，焊接时在电极和铝合金间添加低碳钢板辅助工艺垫片。借助金相显微镜、扫描电子显微镜、能谱仪和万能试验机，研究了点焊接头的组织、力学性能及镍层的作用机理。结果表明，接头界面明显，铝合金侧和钢侧分别形成了鼓状和椭圆形熔核。铝合金侧熔核近熔核线区为树枝晶，熔核中心为等轴晶；双相钢侧热影响区为马氏体和铁素体，熔核中心为较粗大的板条状马氏体。镍中间层可在一定程度上阻止焊接过程中Al-Fe的互扩散，抑制Al-Fe金属间化合物的形成，界面金属间化合物层厚度小于2 μm，接头平均拉剪力达5.17 kN。

Microstructure and Mechanical Properties of Cold Spraying Ni Interlayer Al/Steel Resistance Spot Welding Joints

For the resistance spot welding of 6061-T6 aluminum alloy and DP600 duplex steel, the Ni interlayer was prepared on the surface of Al alloy base material to be welded by cold spraying method before welding, and low carbon steel plate auxiliary process gasket was added between the electrode and aluminum alloy during welding. The microstructure and mechanical properties of spot welding joints and the action mechanism of Ni layer were studied by metalloscope, scanning electron metalloscope, energy disperse spectroscopy and universal testing machine. The results showed that the interface of the joint was obvious, and the Al alloy side and the steel side had formed the bulging and oval nugget respectively. Dendrites were found near melting line of nugget on the side of Al alloy, and equiaxed crystals are found in the nugget center; martensite and ferrite were found in the heat affected zone on the side of the biphasic steel, and massive lath martensites were found in the nugget center. The Ni interlayer could prevent the interdiffusion of Al-Fe to some extent during the welding process, inhibit the formation of intermetallic compounds of Al-Fe. The intermetallic compound layer thickness was less than 2 μm, and the average tensile shear force of the joints was up to 5.17 kN.