Al/Mg异种金属板材电磁脉冲焊接工艺及力学性能研究

Study on Process and Mechanical Properties of Al/Mg Dissimilar Metal Sheet Joints by Magnetic Pulse Welding

目的研究不同工艺参数下铝合金-镁合金磁脉冲焊接接头的微观组织和力学性能。方法利用磁脉冲焊接技术对厚度为1.5 mm的7075铝合金板材和AZ31镁合金板材进行焊接,利用金相显微镜、扫描电子显微镜和万能试验机对焊接接头的微观形貌和力学性能进行测试和分析。结果随着焊接时放电能量的增加,焊接接头的最大拉伸-剪切力呈先增大后减小的趋势,当放电能量为35 kJ时,焊接接头的力学性能最好。通过金相观察结果可知,焊接界面由波形界面和平直界面组成。通过扫描电镜分析可知,无论是波形界面还是平直界面处均发生了不同程度的元素扩散,波形界面处的元素扩散宽度为2μm。结论Al/Mg磁脉冲焊接界面由平直界面和波形界面组成,并且界面处发生了一定程度的元素扩散,波形界面区的元素扩散程度高于平直界面区,这说明磁脉冲焊接的界面是机械结合和冶金结合共同作用的结果。不同工艺参数下的磁脉冲焊接接头具有不同的力学性能,放电能量越大,碰撞速度越大,波形区的长度更长,因而焊接接头力学性能更好,但放电能量超过一定值时,过高的碰撞速度会造成微小裂纹、金属间化合物等缺陷,导致焊接接头的力学性能下降。

The purpose of this paper was to study the microstructure and mechanical properties of Al/Mg magnetic pulse welding joints under different process parameters.The 7075 aluminum alloy sheets and AZ31 magnesium alloy sheets with a thickness of 1.5 mm were welded by magnetic pulse welding.The microstructure and mechanical properties of Al/Mg welded joints were tested and analyzed by metallurgical microscope,scanning electron microscope and universal testing machine.With the increase of the discharge energy,the maximum tensile-shear force of Al/Mg welded joints increased first and then decreased.When the discharge energy was 35 kJ,the mechanical properties of the welded joint were the best.It can be seen from the met-allographic observation that the welding interface was composed of the wave interface and the straight interface.It can be seen that different degrees of element diffusion occurred at both the wave interface and the straight interface through scanning elec-tron microscopy analysis.The element diffusion width at the wave interface was 2μm.The Al/Mg magnetic pulse welding in-terface consists of a straight interface and a wave interface,and a certain degree of element diffusion occurs at the interface.The element diffusion in the wave interface zone is higher than that in the flat interface zone.This indicates that the formation of the interface of magnetic pulse welding is the result of mechanical bonding and metallurgy bonding.The magnetic pulse welding joints under different process parameters have different mechanical properties.The greater the discharge energy is,the greater the collision speed will be,and the longer the length of the wave area will be,so the mechanical properties of the welded joint will be better.However,when the discharge energy exceeds a certain value,the excessively high collision speed will produce defects such as micro cracks and intermetallic compounds,which will cause the decline of the mechanical properties of the welded joint.