基于镁质铆钉的铝合金/镁合金电阻单元焊接接头的组织与性能

Microstructure and properties of resistance element welded joints of aluminum alloy/magnesium alloy welding with a magnesium rivet

受形成于接合界面的金属间化合物的影响,铝合金与镁合金的电阻点焊接头性能难以达到工程应用的要求。为了提高接头的性能、拓宽铝合金/镁合金点焊的应用,分别以腿径为4、6、8与10 mm的镁质铆钉为单元件对AZ31B镁合金与A6061铝合金进行电阻单元焊,并利用扫描电镜观察了接头界面区域的组织,研究了焊接电流和焊接时间对接头抗剪载荷的影响。结果表明:接头中的铆钉帽/上板铝合金、铆钉腿/上板铝合金、上板铝合金/下板镁合金界面处形成了反应物层,主要由Al_(12)Mg_(17)构成,其厚度因位置不同而有所不同。随焊接电流、焊接时间的增大,A6061/AZ61B-REW接头熔核直径增大,抗剪载荷呈先增大后降低的变化趋势;当采用10 mm腿径的铆钉,在焊接电流为25 kA、焊接时间为160 ms以及4.8 kN的电极压力进行焊接时,焊接接头的抗剪载荷最大,约为5.19 kN。

Due to the influence of intermetallic compounds formed at the welding interface,the performance of resistance spot welding joints between aluminum and magnesium alloys is difficult to meet the requirements of engineering applications.In order to improve the performance of the joint and expand the application of aluminum alloy/magnesium alloy spot welding,resistance element welding of AZ31B magnesium alloy and A6061 aluminum alloy was carried out using magnesium rivets with leg diameters of 4,6,8,and 10 mm as element components.The microstructure of the joint interface area was observed using scanning electron microscopy,and the effects of welding current and welding time on the tensile shear load of the joint were studied.The results show that a reactant layer is formed at the interface between the rivet cap/upper plate aluminum alloy,rivet leg/upper plate aluminum alloy,and upper plate aluminum alloy/lower plate magnesium alloy in the joint,mainly composed of Al_(12)Mg_(17),and its thickness varies with different positions.With the increase of welding current and welding time,the diameter of the nugget in the A6061/AZ61B-REW joint increases,and the tensile shear load shows a trend of first increasing and then decreasing.When using a 10 mm leg diameter rivet and welding at a welding current of 25 kA,welding time of 160 ms,and electrode pressure of 4.8 kN,the shear load of the welded joint reaches the maximum value,which is about 5.19 kN.