Influencing Mechanism of Groove Configurations on Microstructure and Tensile Property of Laser Welding-Brazing Al/Steel Joints

Groove configurations are always used in a butt joint by laser welding-brazing. In order to clarify the influencing mechanism of the groove configurations on the interfacial microstructure and tensile property of the joints, a butt Al-on-steel configuration fabricated by laser welding-brazing with various groove grooves was investigated by the electron microscopic analysis, numerical simulation, and tensile tests. The results indicated that the brazing interface consists of Fe-Al and rich Zn intermetallics (IMCs). As the groove angle decreases from 60° to 30°, the average IMCs thickness gradually decreases, the bonding area and maximum tensile strength increases. All the Al/steel joints fail in a mode of brazing-interfacial cleavage. The finite element was employed to simulate the heat transfer process during the welding. The peek temperature shows an identical trend with the IMCs thickness. A large interfacial bonding area at a small groove angle provides abundant heat dissipation media, and causes a low interfacial temperature. The low reaction temperature reduces the diffusion coefficient of Fe and Al atoms, and then decreases the IMCs growth rate. Both the thin IMCs thickness and large bonding area of the brazing interface improve the tensile property of the butt joints.