Influence of surface treatment on microstructure of 2024 aluminum alloy hot compression bonding interface

Three different surface treatments—sandpaper polishing， chemical cleaning， and electrolytic polishing combined with chemical cleaning are employed to conduct hot compression bonding tests on 2024 aluminum alloy. The interface microstructure and the interface healing effect under different surface treatment conditions are investigated using characterization techniques such as OM，SEM， and EBSD. The results reveal that under the three surface treatment conditions， the types of interfacial oxide elements are identical， while variations exist in the quantity and size of the oxides. After holding for 4 h， second-phase particles within the matrix precipitate extensively along grain boundaries and at the bonding interface. For the sandpaper-polished specimen， oxides and second-phase particles at the interface account for approximately 32% of the interface area； this proportion is about 42% for the chemically cleaned specimen， and roughly 28% for the specimen subjected to electrolytic polishing combined with chemical cleaning. Interface healing is achieved through the synergistic action of discontinuous dynamic recrystallization and continuous dynamic recrystallization. Based on the microstructural characteristics of the bonding interface， the interface healing rate is utilized to evaluate the degree of interface healing. After statistical calculations， the order of the interface healing rate is as follows： electrolytic polishing combined with chemical cleaning>sandpaper polishing>chemical cleaning.