镍铝青铜焊丝进行镁/镀锌钢板点焊的焊接性分析*

以镍铝青铜焊丝为填充材料，对AZ31B镁合金/镀锌钢板进行冷金属过渡点塞焊试验研究，分析镁板上孔直径对镁钢点塞焊接头力学性能的影响.并通过分析焊接接头微观组织及其元素分布状况来研究其连接机理。研究结果表明：使用镍铝青铜焊丝能够得到焊缝美观的镁/镀锌钢异种金属的连接接头。镁/钢板焊接接头的焊缝主要由α-Cu和CuAl₂组成，熔合区由镁的固溶体α-Mg以及Al₂Cu₃Mg₂和Mg₂Cu混合的金属间化合物组成。镁板上孔的直径对镁钢接头性能有很大的影响。随着镁板孔径的增大，镁钢点塞焊接头的最大抗拉载荷先增大后减小，且当镁板孔径为5 mm时接头的最大抗拉载荷达到最大为3.4 kN。焊缝金属和镁母材的连接处即熔合区存在大量脆性金属间化合物，使得镁/钢接头整体力学性能较差。

Weldability Analysis of Mg/galvanized Steel Spot Plug Welded Joints with Ni-Al-Cu Cu-based Wire

AZ31B magnesium alloys and galvanized steel sheets are joined by cold metal transfer spot plug welding process with CuAl8Ni6 Cu-based wire based filler wire.The effects of processing parameters and the diameter of the hole in the Mg sheet on mechanical properties are studied.The joining mechanism is achieved by analyzing the microstructure and distribution of elements of welded joints.The results indicate that good weld appearance can be formed for CMT spot plug welded Mg AZ31-galvanized steel joint with CuAl8Ni6 Cu-based wire.The weld metal is composed of α-Cu + CuAl2 eutectic phases,the fusion zone is composed of amounts of brittle intermetallics Al2Cu3Mg2+Mg2Cu phases.The hole diameter in Mg sheet has a major effect on the tensile properties of the Mg-steel joints.With the increase of the hole diameter in Mg sheet,the tensile load firstly increase,then decrease.When the diameter of the hole in Mg sheet reaches 5mm,the maximum tensile load of 3.4kN can be reached.Amounts of brittle intermetallics make the tensile load of Mg-steel spot plug joints become lower.