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

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.