Effect of Welding Processes on Microstructure and Mechanical Properties of Laser-Welded Al-Si-Coated 22MnB5 Steel

Tailor welded blank (TWB) has been developed in the automotive industry to improve structural safety and material efficiency. Al-Si-coated 22MnB5 steel is the main material for laser tailor welding due to its resistance to oxidation and decarburization during hot stamping, which can otherwise deteriorate the performance of welded joints. This study investigates the use of partial ablation welding (PAW) and filler wire welding (FWW) as compared to traditional self-fusion welded (SFW) to enhance the mechanical performances of Al-Si-coated 22MnB5 steel welded joints. The effects of welding processes on the microstructure of welded joints as well as the mechanism of performance enhancement were investigated. Tensile testing results showed that PAW and FWW joints consistently fractured at the base material, whereas the SFW joints fractured at the weld seam. The maximum tensile loads of PAW and FWW joints were, respectively, 12.75 and 12.93% higher than that of SFW joints. Additionally, the microhardness distribution of PAW and FWW joints is uniform with no softening zone. Finally, the study discusses the improved mechanical properties of PAW and FWW joints in terms of microstructural evolution and diffusion of Al elements.