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The diffusion bonding of two dissimilar alloys Aluminum 5083 and Magnesium AZ31 was carried out at 420°C, 430°C,440°C and 450°C for bonding time of 60 min. In order to characterize the microstructure evolution in the joint zone, scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction were applied. The results show that joint formation is attributed to the solid-state diffusion of magnesium and aluminum into Aluminum 5083 and Magnesium AZ31 alloys followed by eutectic formation and constitutional liquation along the interface. At bonding temperature of 430°C diffusion induced grain coarsening was observed at the interface. With increase in bonding temperature, the atomic diffusivity increases, results in easier and speeder chemical bonding. In bonding temperature of 440°C the weld had an irregular shaped region in the weld center, having a different microstructure from the two base materials. The irregular shaped region contained a large volume of intermetallic compound Al 12 Mg 17 and showed significantly higher hardness in the weld center. The present study suggests that constitutional liquation resulted in the intermetallic compound Al 12 Mg 17 in the weld center.Keywords: Diffusion bond / aluminum alloy / magnesium alloy / microstructure / intermetallic Schlüsselwörter: Diffusionsbindung / Aluminiumlegierung / Magnesiumlegierung / Gefüge / intermetallisch Effect of bonding temperature on microstructure and intermetallic compound formation Materialwiss. Werkstofftech.

Dissimilar Friction stir and Diffusion bond welds of Al alloy 5083 and Mg alloy AZ31 were produced. The maximum temperature at the advancing side of friction stir weld rose to a maximum of 435℃. This temperature was selected as the bonding temperature, for diffusion bonding of these two alloys. The diffusion bonding time was 60 min. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate the compositional changes across the joint region. Dissimilar FS weld, produced layers of new phases of Al 12 Mg 17 and Al 3 Mg 2 intermetallics. DB weld, produced a melted-andsolidified eutectic structure consists a hypo-eutectic structure in the middle of the joint and a two layer structure between the eutectic and the Al base. The shear strength of joint corresponding to DB welded specimen was 43.2 MPa. The tensile strength of joint corresponding to FS welded specimen was 51.3 MPa. The present study suggests that constitutional liquation resulted in the intermetallic compound formation in the weld center.