Effect of Zn interlayer on brazeability of AZ31B–Mg alloy to steel sheet

The brazeability of AZ31B–H24 magnesium alloy sheet to Zn electroplated, plain carbon steel sheet using an Mg–Al–Zn alloy filler metal and a diode laser heat source has been investigated. While the Zn coating promoted good wetting between the molten filler alloy and the steel sheet, it did not play a direct role in forming the final bond. Bonding between the magnesium alloy and the steel was facilitated by the formation of two transition layers. First, a nanoscale layer of FeAl 3 phase formed on the surface of the steel by diffusion of Al from the Mg–Al–Zn brazing alloy into the steel. Upon further cooling, nucleation and growth of either α-Mg+MgZn eutectic phases or Mg 2 (Al,Zn) 3 phase occurred on the FeAl 3 surface layer.