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

Abstract

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)–Al11(Mn, Fe)4 intermetallic compound layer and approximately 350 nm–thick α–Fe(Al) solid solution. The orientation relationships (OR) of α–Fe(Al)/HT–Al11(Mn, Fe)4 system and Mg/HT–Al11(Mn, Fe)4 system matched favorable with (011)α–Fe(Al)||(060)HT–Al11(Mn, Fe)4 and [11̅0]α–Fe(Al)||[100]HT–Al11(Mn, Fe)4, (011¯2)Mg||(060)HT–Al11(Mn, Fe)4 and [101¯0]Mg||[100]HT–Al11(Mn, Fe)4, respectively. The growth model of the interface layer along the Mg/steel interface was discussed.