Effect of Cooling Rate on the Microstructure and Mechanical Properties of Cu/Al Bimetal Fabricated by Compound Casting

Cu/Al bimetal was fabricated successfully by compound casting at different cooling rates in the range from 0.8 K/s to 1.83 K/s (0.8 °C/s to 1.83 °C/s). Interfacial cooling curve, microstructure evolution, bonding strength, and interfacial formation mechanism of Cu/Al bimetal were investigated simultaneously. Results show that the transition zone consists of the intermetallic compounds (IMCs) and the remelting zone. The IMCs are identified as Al₄Cu₉, AlCu, and Al₂Cu, types of which are not affected by the cooling rate. The cooling rate primarily influences the thickness of IMCs, the microstructure of the remelting zone, and the morphology of the remelting zone/Al interface. The Cu/Al bimetal produced at the cooling rate of 1.02 K/s (1.02 °C/s) has relatively higher bonding strength than those at the cooling rates of 0.8 K/s and 1.83 K/s (0.8 °C/s and 1.83 °C/s). Shear fracture primarily occurs on the hard brittle IMCs rather than on the remelting zone. Based on the cooling curve and diffusion analysis, a new bonding mechanism of Cu/Al bimetal is proposed.