Abstract
Brazing of copper to aluminum using Al-Si alloy has been carried out in a resistance furnace. Microstructure and properties for Cu/Al brazing joint were studied by metallography, scanning electron microscope (SEM) and INCA energy disperse spectroscopy. Experimental results obtained showed that a reliable joint could be formed with the technology parameters: brazing temperature T = 610 °C∼625 °C, holding time t = 2∼3 min and pressure P = 0.4∼0.8 MPa. An obvious transition layer of intermetallic (IMC) with a thickness about 10 µm was formed near the interface of copper and the brazing alloy. Eutectic phase α(Al)-CuAl₂ and needle-like precipitates (AlCuSi phase) were found in the brazing seam region. Furthermore, an external pressure was helpful to the brazing progress, however, microhardness in the brazing seam region was too high with a big external pressure. A peak point of microhardness was found at the interface of Cu/Al brazing joint, and the transition layer of IMC phases became the initiation and propagation channel of micro cracks.

Key words
Al/Cu joint, interface, microstructure, microhardness, cracks

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