On the diffusion brazing of Al-Si alloy castings

Abstract

The diffusion brazing process in which the liquid filler metal is formed by mutual diffusion between the brazement and the insert metal in a brazing cycle was applied to joining Al-Si alloy castings. When the brazement of Al-Si alloy castings with a copper insert metal is heated up to the ternary eutectic point of Al-Cu-Si system at 525°C, a ternary eutectic Al-27%Cu-5%Si alloy will be formed at the interface to act as a brazing filler metal. The diffusion brazing process seemed to be suitable for brazing the Al-Si alloy castings from the viewpoints of good brazability and uniform structure of brazed joint. The brass insert metal is more beneficial than copper on lowering brazing temperature.