Abstract: Process and mechanism of aluminum eutectic contacting reaction brazing is studied by using a scanning electron microscope and an electron probe. The formation process of the eutectic reaction layer can be divided into three stage; the first is the diffusion and dissolution between atoms; the second is the composition homogenization; the third is isothermic solidification of the eutectic reaction layer. The results show that the Cu on the grain boundary of base metal Al must come from the solid atoms through diffusion of the Cu. After the eutectic ingredients is accumulated a binary low melting point eutectic substance is formed at the grain boundary. The eutectic reaction brazing of Al is formed.

Key words: Aluminum, Brazing, Eutectic reaction