Investigating the microstructural evolution and interfacial morphology of laser- and arc-brazed ZnAlMg coated steel

ZnAlMg coatings are highly corrosion resistant due to their unique microstructure and have shown promise as a next-generation coating material for automotive structures. Despite the extensive research conducted on the corrosion behavior of these coatings, the microstructural evolution of the coatings during further manufacturing processes, such as welding and brazing, has not been fully explored. This study presents a comprehensive assessment of the impact of heat source on the microstructural evolution and interfacial morphology of laser- and arc-brazed ZnAlMg coated steel using a CuSi3Mn filler material. The results showed that although a high density of FeSi(Cu) precipitates was detected at the center of the arc-brazed specimen, a limited number of precipitates were observed in the same region of the laser-brazed specimen. It was shown that the arc-brazed sample had a solid solution structure with a high degree of Zn and Cu gradient at the tail region. In contrast, the laser-brazed specimen showed a distinct microstructure in the same area with eutectic structures, a dendritic transition zone, and a Cu-based microstructure. The present work provides new insight into developing the application of ternary ZnAlMg coatings in the automotive industry.