The mechanical properties and interface bonding mechanism of immiscible Mg/steel by laser-tungsten inert gas welding with filler wire

Immiscible Mg/steel was welded by laser-tungsten inert gas (TIG) butt fusion welding method with AZ61 filler wires. A better joint was obtained by optimizing the process parameters. The tensile strength of Mg/steel joints was improved with the increase of laser power before the weld burn-through. The interface bonding strength reached 238.1 MPa, about 94.5% of AZ31 base metal, and the joint fractured approaching Mg/steel interface. The Mg/steel interface layer was mainly composed of a continuous 50 nm-thick high temperature (HT)-Al-11(Mn, Fe)(4) intermetallic compound layer and approximately 350 nm-thick alpha-Fe(Al) solid solution. The orientation relationships (OR) of alpha-Fe(Al)/HT-Al-11(Mn, Fe)(4) system and Mg/HT-Al-11(Mn, Fe)(4) system matched favorable with (011)alpha-Fe(Al) vertical bar vertical bar (060)HT-Al11 (Mn, Fe)4 and [1 (1) over bar0]alpha-Fe(Al)vertical bar vertical bar[100]HT-Al11(Mn, Fe)4, (01 (1) over bar2)mg vertical bar vertical bar(060)HT-Al11(Mn, Fe)4 and [10 (1) over bar0]Mg vertical bar vertical bar[100]HT-Al11(Mn, Fe)4, respectively. The growth model of the interface layer along the Mg/steel interface was discussed.