Effect of line spacing on nanosecond pulsed laser welding of AZ31B magnesium alloy and 304 stainless steel

Nanosecond pulse laser welding was performed on AZ31B magnesium alloy and 304 stainless steel. The study explored the effects of varying line spacing on the weld joint morphology, microstructure, and fracture properties, while keeping other parameters constant. The temperature field during the magnesium/steel laser welding process was simulated using COMSOL software. Results indicated that when the line spacing was 0.04 mm, the welding surface exhibited cracks and a significant amount of oxides due to excessive heat input. However, at a line spacing of 0.2 mm, there were fewer defects and a larger bonding area at the interface. As line spacing increased, the path for heat conduction between welds became longer, leading to a reduction in thermal interaction between adjacent welds and poorer welding performance. Shear force test results showed that the fractured shear force was achieved at a line spacing of 0.2 mm. Additionally, the fracture modes were classified as matrix embrittlement failure (MEF), substrate tearing failure (STF), and interfacial failure (IF).