Effect of welding speed on Nd:YAG laser weldability of ZE41A-T5 magnesium sand castings

摘要

The 2-mm butt joints of ZE41A-T5 sand castings were laser welded using 1.6 ram EZ33A-T5 filler wire and a continuous wave Nd:YAG system at a power of 4 kW, surface defocusing and various welding speeds. Compared with the base metal, the fusion zone showed significant grain refinement due to high cooling rate. No grain coarsening was observed in the heat affected zone (HAZ). The porosity area percentage and total solidification crack length in the fusion zone (FZ) were reduced as the welding speed increased from 4 to 7 m/min. Fusion zone area, total penetration depth, and weld width decreased with increased welding speed. The hardness in the FZ was similar to or higher than the base metal after a natural aging of about one year, but there was a drop in the hardness of the HAZ. The HAZ width decreased with increasing the welding speed. Tensile test showed that a joint efficiency of approximately 75 - 90 percent was obtained.