Microstructure Evolution and Interfacial Reactions in Laser Beam Welded Fe–Al Joints

Abstract This study investigated laser beam welding of dissimilar steel and aluminum alloy in a lap configuration. The effects of defocusing distance and heat input on weld quality were examined. A defocusing distance of + 10 mm resulted in desirable weld characteristics. Using a 3.8 kW (38 J/mm) heat input produced weld seams with minimal defects. XRD analysis identified Fe 2 Al 5 , FeAl, Fe 3 Al, and FeAl 3 at the Fe-Al joint interface. The formation mechanism of Fe-Al intermetallic compounds is explained in detail. The weld seam with 38 J/mm heat input achieved the best joint performance, with a tensile load of 0.922 kN and elongation of 0.656 mm, surpassing those at 36 J/mm and 40 J/mm. The findings provide valuable insights into optimizing laser welding parameters and controlling intermetallic compounds formation, both of which are crucial for enhancing the strength and reliability of steel–aluminum joints.