Interfacial microstructure characterization and solderability of the low pressure cold sprayed Cu-Al₂O₃ coating on Al substrate

A solderable coating was formed by low pressure cold spraying the Cu-Al₂O₃ particles upon the Al substrate. The metallurgical bonding at the interface between the cold sprayed copper layer and the Al substrate was confirmed by FIB-SEM and HR-TEM. A considerable number of stacking faults and twins were observed near the Cu interface due to plastic deformation caused by the compressive shock, while a large number of dislocations were observed near the Al interface. An atomic diffusion layer of about 100 nm was found, which includes an ordered lattice structure (AlCu₃), a severely deformed lattice structure, and an amorphous region surrounded by Cu and Al lattices.