Microstructure and mechanical properties of nanosecond pulsed laser welded Al–Cu–steel laminated structures

Abstract

Al-Cu-steel laminated structures with configurations of Al/Cu/steel and steel/Cu/Al were obtained via nanosecond pulsed laser welding. Cavities occurred at the bottom welds in two joints. Full-penetration welds occurred more easily in steel/Cu/Al joints compared to Al/Cu/steel joints. The metallurgical reaction of Al and Fe was impeded by Cu. The eutectic (α-Al+θ ) and θ -CuAl 2 phases were predominant at the Al/Cu interface in the steel/Cu/Al joints, while (Cu, Fe) was the main phase in Al/Cu/steel joint. The average lap shear force of the Al/Cu/steel joints (51.2 N) was superior to that of steel/Cu/Al joints (37.2 N). The fracture for both joins occurred at the Al/Cu interface. The fracture morphologies indicated that smaller connection width and Al/Cu IMCs caused the weld pullout failure (WPF) mode in steel/Cu/Al joints. The larger connection area and presence of (Cu, Fe) solid solution were responsible for the interfacial shear failure (ISF) mode in Al/Cu/steel joints.