Abstract: Effects of annealing temperature and time on the microstructure, hardness and interfacial bonding strength of copper-clad aluminum composite flat strips formed by continuous casting and rolling were studied. The results show that when annealed at 150 ℃ and 200 ℃ for 60 min, the copper cladding occurs only recovery, and the hardness is about 120 HV0.025. Recrystallization begins at 250 ℃, and complete recrystallization occurs at 350 ℃, and the hardness drops to 61 HV0.025. When annealed at 150-250 ℃ for 60 min, the aluminum core only occurs recovery, and the hardness is about 45 HV0.025. Recrystallization begins at 300 ℃, complete recrystallization occurs at 350 ℃, and the hardness drops to 23 HV0.025. With the annealing temperature increases from 150 ℃ to 300 ℃, the thickness of Cu-Al interfacial layers increases from 0 to 1.0 μm, and the interfacial bonding strength decreases from 75.0 MPa to 66.0 MPa. When the annealing temperature rises to 350 ℃, the thickness of interface layers increases rapidly. The thickness of interface layers at 400 ℃ is 7.6 μm, and the interface bonding strength is 45.7 MPa. When annealing at 300 ℃, with the annealing time extends from 10 min to 90 min, the recrystallization degree of the copper cladding increases gradually, and the hardness decreases from 120.3 HV0.025 to 63.8 HV0.025. After the annealing time reaches 90 min, the microstructure is partially recrystallized. The microstructure and hardness have little change when annealing time is further extended. With the annealing time extends from 10 min to 120 min, the recrystallization degree of aluminum core is slightly increased, and the hardness is reduced from 41.3 HV0.025 to 33.8 HV0.025. The thickness of the Cu-Al interfacial layers increases from 0.2 μm to 1.3 μm, and the interfacial bond strength decreases from 80.0 MPa to 62.3 MPa.

Key words: Cu-Al composites, annealing, interface, grain, hardness