A novel brazing technique for aluminum and other metals

In this brazing technique, at least one of the metal surfaces to be joined is coated with a powder-mixture of silicon and a potassium fluoroaluminate flux. Brazing of aluminum is carried out by heating at ∼600 °C in nitrogen gas. During heating, the flux melts and dissolves the oxide layers on the contacting surfaces, thus allowing the silicon to come into intimate contact with bare aluminum. At a temperature exceeding the Al–Si eutectic temperature of 577 °C, the silicon diffuses rapidly into the aluminum and generates in situ a layer of Al–Si liquid alloy of near-eutectic composition. The filler material then flows into the joint and forms a fillet. This brazing technique may be exploited with aluminum using intermediary elements other than Si, and may be used for joining a variety of metals.