基于添加Zn中间层的汽车用镁/铝异种金属电阻点焊工艺与性能研究

Study on Process and Properties of Mg/Al Dissimilar Metal Resistance Spot Welding for Automobile Based on Adding Zn Intermediate Layer

采用电阻点焊并添加Zn中间层对汽车用镁合金和铝合金进行焊接,通过金相显微镜、扫描电镜和万能试验机研究了焊接接头组织和性能。结果表明,添加Zn中间层后,汽车用镁合金和铝合金电阻点焊时两侧母材分别与Zn发生反应,Zn的加入阻止了镁铝的直接接触,铝侧断口主要物相为Al、MgZn_2和Al_5Mg_(11)Zn_4,镁侧断口主要物相为Mg、MgZn_2,断裂发生在MgZn_2处。随着焊接电流或焊接时间的增加,添加Zn中间层的汽车用镁/铝异种金属焊接接头拉剪力先增加后减小,焊接电流25 kA、焊接时间500 ms、焊接压力8 kN时,接头拉剪力达到最大值4.93 kN。

Mg alloy and Al alloy were welded by resistance spot welding with adding Zn interlayer. The microstructure and properties of the welded joints were studied by metallographic microscope, scanning electron microscope and universal testing machine. The results show that both sides of the matrix metal react with Zn interlayer when spot welding of Mg alloy and Al alloy, and the addition of Zn can prevent the direct contaction of Mg and Al. The main phases on the aluminum fracture side are Al, MgZn_2 and Al_5Mg_（11）Zn_4, and the main phases of magnesium fracture side are Mg and MgZn_2. The fracture occurs in the MgZn_2 layer. With the increase of welding current or welding time, the shear force of the welded joints increases firstly and then decreases. The maximum value of shear force of welded joints is 4.93 kN under the welding current of 25 kA,welding time of 500 ms and welding pressure of 8 kN.