Joining of aluminium sheets by combined solid state and TLP bonding processes

Abstract

Our effort is to develop an innovative process to join Al sheets at moderate temperatures (200–300°C) by accumulative roll bonding (ARB) combined with transient liquid phase bonding utilising Ga. Solid state joining of Al is limited by the surface Al2O3 that hampers the Al atom diffusion despite the intimate contact between the metal sheets. Mechanical brushing of the Al2O3 improves bonding. Our approach uses ARB to break the brittle Al2O3 by roll bonding two sheets. Strips of 1100-Al were cut, cleaned coated with a thin film of Ga and then preheated before rolling. The Ga coated Al strips roll bonded at 200°C showed greatest strengths, but processing at 300°C resulted in lower strengths with evidence of liquid metal embrittlement. The undamaged Al2O3 prevents liquid Ga from contact with the Al metal.