Effect of welding speed on butt joint quality of laser powder bed fusion AlSi10Mg parts welded using Nd:YAG laser

The invention of additive manufacturing technology, such as laser powder bed fusion, was initiated by the aerospace industries' growing need for lightweight alloy components with intricate geometries. However, widespread adoption of lightweight alloy components is limited by size restrictions. Currently, only relatively small and simple-shaped objects can be efficiently produced using lightweight alloys. Thus, this research aims to investigate the effect of welding speed on butt joint quality of laser powder bed fusioned AlSi10Mg parts welded using an Nd:YAG laser. Laser beam welding is a method for welding small parts manufactured by laser powder bed fusion together to build large-scale and complex-shaped objects. Using a 2 kW continuous wave solid-state Nd:YAG laser with three different weld scan speeds (150, 175, and 200 mm min-1), autogenous, single-pass, square butt joints were created from 3 mm thick plates. Crystal orientation mapping and fractography results showed that the laser beam welding scan speed significantly impacts plastic deformation and fracture behavior. A significant amount of grain refinement and an Si-particle morphology change was realized in the weld zone's microstructure, attributed to the increase in weld scanning speed. The transverse tensile test demonstrates that increasing the weld scan speed from 150 to 200 mm min-1 leads to significant growth in the efficiency of the weld joint, from 70 % to 77 %, arising from grain refinement (13-8 mu m). However, a significant decrease in ductility is observed with increasing scan speed. In addition, it was determined that pores have substantial effect on tensile strength and ductility.