Predicting susceptibility of magnesium alloys to weld-edge cracking

The use of Mg alloys for vehicle weight reduction has increased significantly recently. Because the potential of metal inert gas (MIG) welding as a versatile process for mass producing Mg welds has increased dramatically recently, the need for better understanding the weldability of Mg alloys in MIG welding also increases. Although the susceptibility of Mg alloys in MIG welding to cracking along the weld edge has been reported, it has not been studied. The present study investigated the susceptibility of Mg alloys to weld-edge cracking using the circular-patch welding test and MIG welding. A Mg circular patch of one chemical composition was placed inside and butt welded to a tightly clamped Mg workpiece of a different composition. Circular-patch welds were made between the most widely used Mg casting alloy AZ91, the most widely used Mg wrought alloy AZ31, and pure Mg with three different Mg filler wires AZ31, AZ61 and AZ92. The susceptibility to cracking along the weld edge was predicted and compared against the experimental results. Such a prediction has not been made for welds between different (dissimilar) materials, which is more difficult than that for welds between identical materials.