Reinforcement effect of Mg—Al—Zn ternary IMC on MB8/2024 joints with Al/Zn/Cu/Zn multi-interlayer via ultrasonic-assisted brazing

The evolution of microstructure in the MB8/2024 dissimilar alloy joints by using Al/Zn/Cu/Zn multi- interlayers via ultrasonic-assisted brazing was investigated. The results show that the addition of aluminum foil on the MB8 side realized the transformation of Al3Mg2 binary intermetallic compounds (IMCs) to AlMg4Zn11 ternary IMCs along the interface between copper foil and MB8 magnesium alloys. This transformation reinforced the joints and then the shear strength reached a maximum at 22 s (85.26 MPa). Thermodynamic analysis shows that ΔGMg,Al,Zn of AlMg4Zn11 (–38.65 kJ/mol) was smaller than that of Al3Mg2 (–31.94 kJ/mol), which provided a basis for the IMC transformation. Mg32(Al,Zn)49 quasicrystal was found for the first time using ultrasonic-assisted brazing due to the cavitation effect.