Study on microstructure and properties of Mg/steel laser welding-brazing joint assisted by alternating magnetic field with Ni interlayer

Abstract

The laser welding-brazing technology assisted by alternating magnetic field was adapted to Mg/steel dissimilar materials with Ni interlayer. Microstructure and mechanical properties of joints were compared with and without alternating magnetic field. The results showed that the weld width L was enlarged and ensured good weld formation and weld quality by applying the alternating magnetic field. The joint was comprised of Mg side weld zone, intermetallic compound (IMC) layer and steel side weld zone. The effect of mechanical occlusion was enhanced by the appearce of zonal structures of Fe–Ni solid solution in the Mg side weld zone and the serrated Mg2Ni in the brazing zone of IMC layer. A continuous nano scale AlNi layer formed in the fusion welding zone of IMC layer, which is conducive to strengthen the joint. The optimal joint assisted by appropriate alternating magnetic field was obtained with tensile and shear strength enhanced by nearly 15%.

Keywords

• Laser welding-brazing technology
• Alternating magnetic field
• Mechanical occlusion
• Tensile and shear strength