Microstructure and mechanical properties of magnesium alloy AZ31B joint brazed with Al-Mg-Zn filler metal

High-frequency induction brazing of wrought magnesium alloy AZ31B with Al-Mg-Zn filler metal was investigated. Microscopic structure, the phases and the mechanical properties of brazed joint were studied. The microstructure and formation phases at the interface in the brazed joint were investigated by scanning electron microscopy(SEM), X-ray diffraction instrument(XRD) and energy dispersive spectrometer (EDS). The strength of the brazed joint and the microhardness of the formation phases were also tested. The results show that, Al-Mg-Zn filler metal reacting with the base metal AZ31B, and α-Mg+β-Mg17(Al, Zn)12 divorced eutectic structure is formed in the brazed joint. Microhardness of the base metal AZ31B is the smallest and β-Mg17(Al, Zn)12 phase of the brazed joint is the hardest. Both the butt joint and the overlap joint exhibit intergranular fracture mode, the fracture comes from hard brittle phase β-Mg17(Al, Zn)12 of α-Mg+β-Mg17(Al, Zn)12 divorced eutectic structure.