Effect of electrical current on the morphology and kinetics of formation of intermetallic phases in bimetallic aluminum-copper joints

The effect of electrical current on the morphology and kinetics of formation of intermetallic compounds of bimetallic friction welded aluminum-copper joints was studied. The formation and growth of intermetallic compounds was studied in the temperature ranges 200-500/spl deg/C that was realized by heating Al-Cu joints with an AC current of different intensities (400-1000 A). The presence of an electrical field greatly accelerates the kinetics of formation of intermetallic phases and alters significantly their morphology. The formation and growth of intermetallic phases exerts a pronounced effect on the mechanical (microhardness) and electrical integrity of aluminum-copper joints. The contact resistance increases linearly with the thickness of the intermetallics. The phases formed are very hard and extremely brittle. The growth kinetics of intermetallic phases under the influence of electrical current is much higher than that under diffusion annealing in furnace.