Influence of Bonding Temperature on Microstructure and Mechanical Properties of AZ31/Zn/Sn/5083 Diffusion Joint

Diffusion bonding with an interlayer is considered an effective means of obtaining Mg/Al dissimilar alloy joints. However, at low temperatures, it is often impossible to simultaneously achieve joints between the interlayer and Mg/Al under the same bonding parameters. For this reason, the interlayer is usually prefabricated on the substrate, followed by conducting diffusion bonding. Due to the higher diffusion rate of atoms in the liquid phase compared to atoms in the solid phase, creating a liquid phase field in diffusion bonding to reduce diffusion resistance and thus omitting the step of prefabricating the interlayer is a feasible approach. In this study, solid-state diffusion bonding and TLP (transient liquid phase) diffusion bonding were combined. The low-temperature diffusion bonding of the Mg/Al alloy was achieved under the same parameters using a Zn/Sn composite interlayer, utilizing the formation of a Zn-Sn eutectic liquid phase and the complete melting of Sn during heating without requiring a prefabricated interlayer. Unlike conventional composite interlayers used in diffusion bonding, the Sn layer of the Zn/Sn composite interlayer completely melts into liquid and is squeezed out of the bonding interface at the bonding temperature. The Mg/Zn interface was bonded by solid-state diffusion bonding, while the Al/Zn interface was joined through TLP diffusion bonding. Research on the bonding temperature showed that the bonding temperature range was narrow and that variation in the bonding temperature had a significant impact on the microstructure of the joints.