Influence of Ni interlayer width on interfacial reactions and mechanical properties in laser welding/brazing of Al/Mg lap joint

Laser welding/brazing of AA5182 Al to ZEK100 Mg in a lap joint configuration was performed by using a Ni interlayer. The stick-out width of Ni interlayer (WNi) had significant effects on the weld appearance, interfacial microstructure and joint strength of laser Al/Mg joints. Weld defects including porosity and crack were largely reduced with the increase of WNi from 2 to 6 mm, but a fracture occurred at the Mg/Ni interface when it increased to 8 mm which led to an immediate failure after welding. Mg–Al, Mg–Ni and minor Al-Ni IMCs were observed at the Mg/Ni interfacial region. The joint strength first increased and then decreased with the rising WNi, which was mainly determined by the width of Mg-Ni IMCs.