Abstract: Experiments of TIG welding-brazing of AZ31B magnesium alloy and PRO500 steel were carried out to investigate the effect of heat input on the microstructure and mechanical properties of lap joints. The results indicated that a effective bonding achieved between AZ31B magnesium alloy and PRO500 steel by TIG welding-brazing method. Under a optimized current process parameters, the strength of the joint could reach 85% of the Mg alloy base metal. The transition zone in the interface was formed including the formation of the Fe-Mg-O compounds, the AlFe3 intermetallic compound (IMC), and the cross diffusion of the elements Fe and Mg from the substrate. The fracture mode of AZ31B/PRO500 joint presented a mixed-rupture characteristics of quasi-cleavage and tearing at a smaller heat input. With the increase of welding current, the fracture mode changed to a brittle rupture with the lea-ding role of the quasi-cleavage fracture. Then the bonding strength decreased obviously.
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2017, Vol. 31 
