Joining mechanisms of Mg-steel butt welded joints by cold metal transfer method

In this paper, Mg AZ31 sheet and galvanized steel sheet were butt welded and joined by cold metal transfer method with AZ61 Mg wire. Weld appearance, tensile properties and microstructure of Mg-steel butt joints at various welding parameters were investigated by changing wire feed speeds and groove angles. Results indicated that Mg-steel brazed-welded joints with good weld appearance and 4.02kN of tensile load can be achieved. And the brazed-welded joint is composed of welded joint at Mg side and brazed joint at steel side. The brazed joint is made of two parts, one is Mg-galvanized steel brazed joint which is located at the top of galvanized steel sheet, and the other is Mg-bare steel brazed joint which is located at the groove side. The Mg-galvanized steel joint brazed interface is composed of two reaction layers with -Mg+MgZn eutectic phase and Fe/Al reaction layer. The Mg-bare steel brazed interface at the groove side is composed of Fe/Al reaction layer, and Fe/Al phase is diffused and reacted by Al element of the Mg wire and Mg base metal.