Study on the Thermal Conductivity of Cu/Al Joints with Different Interfacial Microstructures

Three types of Cu/Al joints with different interfacial microstructures prepared by diffusion bonding, friction stir welding, and explosive welding were obtained, and the interfacial thermal conductivity was emphatically discussed in this paper. Two layers of intermetallic compounds with a width of 5∼12 μm were formed in the joint prepared by diffusion bonding. And a mixture of a supersaturated solid solution and few dispersed compounds with a thickness less than 1 μm was formed in the friction stir welding Cu/Al joint. The bonding interface of the Cu/Al explosive welding joint presented a wavy-like morphology with a width of 300∼350 μm. The interfacial thermal conductivity with different interfacial microstructure was calculated analytically using the acoustic mismatch model and compared with the measured value of the joints. The interfacial thermal conductivity mainly depends on the type of interfacial phase and its thickness. The calculated result showed that the interfacial thermal conductivity of friction stir welding joint was the highest (1∼8 × 107 W m−2·K−1). The experiment results suggested that the interfacial thermal conductivity showed the trend that explosive welding < friction stir welding < diffusion bonding.