Cold metal transfer (CMT) welding was used to lap the dissimilar metallic sheets of magnesium alloy AZ31B and galvanized steel plate HDG60, and three magnesium wire AZ92, AZ61,AND MnE21 were employed in the welding experiment. The result showed that a better weld could be formed with these wires in the case of appropriate welding parameters. However, the welding window of the AZ92 and AZ61 was wider, and that with MnE21 was narrower and noticeable cracks took place at the weld. It was shown by the analysis of joint interface microstructure that the joint would be divided into weld zone, brazing zone, and fusion zone. It resulted from the analysis of X-ray diffraction that, when the magnesium welding wire of AZ92 and AZ61 was employed, there could mainly be magnesium solid solution and such compounds as MgFeAlO4, Mg2Zn11 , and Al12Mg17 in the welding joint interface. When MnE21 was used as welding wire, there would basically be Mg solid solution and compounds Mg32Al49 and Al12Mg12 there. The results showed that the tensile sheerload of the joint reached 87. 5% of the magnesium base material with same dimensions when AZ61 wire was used. When other two Mg wires were used, the tensile sheer load would be less. In short, AZ61 wire would be more suitable for joining dissimilar metals between the magresium and steel.%采用CMT冷金属过渡焊对异种金属AZ31B镁合金板和HDG60镀锌钢板进行焊接,试验中采用AZ92、AZ61、MnE21镁合金焊丝.结果表明:在合适的工艺参数下,3种焊丝都能形成较好的焊缝,但AZ92、AZ61焊丝的焊接窗口比较宽,而MnE21焊丝的焊接窗口极窄,并且焊缝处有明显的裂纹.接头的界面组织分析表明,焊接接头被分成焊缝区、中间结合区、熔合区.通过X射线衍射分析得出,当采用AZ92、AZ61镁合金焊丝时,焊接结合面主要有Mg的固溶体,还有MgFeAlO4、Mg2Zn11、Al12 Mg17等化合物；采用MnE21镁合金焊丝时,焊接结合面主要有Mg固溶体,还有Mg32 Al49、Al12Mg17化合物.在拉伸试验中.采用相同规格的拉伸试样,使用AZ61焊丝的接头拉剪力可达镁母材的87.5％.而采用其他2种焊丝时拉剪力较小.由此可见,AZ61焊丝更适合焊接镁钢异种金属.
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