Al/steel joining by MIG welding with high frequency heating

6061 Al alloy and commercial steel were joined via the metal inert gas welding (MIG) with auxiliary high-frequency heating. The influence of parameters on the weld appearance and intermetallic compound layer was studied. The results showed that the increase of the high-frequency current voltage and MIG voltage made the intermetallic compounds layer thicken. The appearance of the weld was improved first and then deteriorated when the high-frequency electric voltage was raised. Interfacial tensile strength was relatively high when the interfacial compounds layer was 1 mu m to 5 mu m thick. Fracture analysis showed that the brittle fracture of the interfacial compound layer was the key factor that affected the joint tensile strength. Optimal process window was suggested: the heat input range of the high-frequency current was 720-810 J/cm, and that of MIG was 575-615 J/cm. The optimal joint presented more than 70% tensile strength of the 6061 Al.