Influence of Pure Aluminum and 7075 Aluminum Alloy Powder Interlayers on the Microstructural and Mechanical Properties of Diffusion-Bonded 7B04 Aluminum Alloy Joints

Diffusion bonding (DB) of aluminum alloys faces significant technical challenges, requiring thorough surface preparation and precise control of process parameters. To enhance the joint quality of 7B04 aluminum alloy sheets, pure aluminum (Al) and 7075 aluminum alloy powders were used as interlayers. In the DB experiments, nano-sized Al powder and micro-sized 7075 powders with different particle sizes served as interlayer materials. Compared to DB without an interlayer, using powder interlayers substantially reduced the bonding temperature while improving overall joint performance, with deformation kept below 6%. The lap shear strength (LSS) of the bonded 7B04 joints was significantly higher when 45 μm and 75 μm 7075 powders were used, compared to the 5 μm 7075 powder. The joint with a 50 nm Al powder interlayer achieved a maximum LSS of up to 220 MPa and exhibited considerably higher microhardness. Additionally, the mixed Al/7075 powder interlayer effectively decreased voids at the joint interface, contributing to increased LSS.