On the Correlation Between Thermal Cycle and Formation of Intermetallic Phases at the Interface of Laser-Welded Aluminum-Steel Overlap Joints

A laser beam welding process via heat conduction was applied to join DC01 steel with aluminum (Al) in overlap configuration without filler wire. The effect of the applied laser power (1.7, 1.8, 2.1, and 2.4?kW) on the formation and evolution of the interfaces between steel and Al was analyzed. Two intermetallic compounds were found at the interface, namely, one adjacent to the steel layer (Al5Fe2) and one close to the solidified Al (Al13Fe4). The thickness of the intermetallic reaction layer increases with laser power, while the morphology of its individual components evolves due to differences in accumulated thermal cycles. Correlations between simulations and measurements show that the peak temperature has significantly stronger influence on the thickness of the intermetallic reaction layer than cooling time and the integral of temperature over the time. Shear/tensile strength tests reveal that all the specimens fail in the Al heat affected zone.