Effects of welding wire composition on the repair welds of sand-cast Mg-Gd-Y alloy: Microstructure and mechanical properties

Cast defects could severely deteriorate the quality of magnesium alloy component. Repair welding is an efficient and economic method to improve the casting qualification. In this study, the impact of welding wire composition on the microstructures and mechanical properties of Mg-Gd-Y repair welds was investigated. The results illustrated that, the Zr in the Mg-6Gd-3Y-0.5Zr (VW63K) welding wire promoted the grain refinement in the fusion zone (FZ) of the repair weld, and VW63K FZ performed better thermal stability when subjected to 500 ? for 6 h, because the grain boundaries migration in VW63K FZ was hindered by Zr-contained particles, while the Mg-6Gd-3Y (VW63) FZ presented dramatic grain coarsening. Under as-welded, T4 and T6 conditions, the joint efficiency of VW63K repair weld was 127.64%, 113.14% and 107.37% respectively, while that of VW63 repair weld was 121.61%, 94.92% and 91.67%, respectively.