Microstructure and phase constituents in the interface zone of Mg/Al diffusion bonding

The microstructure and phase constituent for the Mg/Al diffusion-bonded joint were studied via scanning electron microscope (SEM), microhardness test, electron probe microanalyzer (EPMA), and X-ray diffraction (XRD). The test results indicated that the new compact phase was formed near the transition region of the Mg/Al diffusion interface. There are three new phase layers in the transition region. The microhardness of the diffusion zone is higher than that of the Mg and Al substrate. The fracture morphology mainly consists of a coarse and gray fracture, and the fracture is mainly the mixed fracture of cleavage and intergranular. X-ray diffraction tests indicate that the diffusion zone of the Mg/Al diffusion-bonded joint consists of intermetallic compounds MgAl, Mg₃Al₂, and Mg₂Al₃. With the increase of temperature, the content of Mg₃Al₂ and Mg₂Al₃ phases with good stability was increased.