Diffusion Bonding of Superplastic 7075 Aluminum Alloy

ABSTRACTBecause of the presence of surface oxide films, aluminum alloys are very difficult to join by diffusion bonding processes when there are no interlayers between mating surfaces. In the present investigation, the diffusion bonding of superplastic 7075 aluminum alloy has been carried out using a special method for surface treatment in the temperature range 500∼520°C, at pressures of 2.07∼3.OMPa, times of 90∼150min and a vaccum of 1×10−5torr. The joint strength obtained is the same as the base metal strength of the alloy, and the joint microstructure is indistinguishable from that of the base metal. In this paper, the effect of the superplastic treatment of the alloy on the bonding process is discussed, and it is proposed that the bonding mechanism is the migration of the initial bond interface caused both by the diffusion of atoms and by the growth of grains during the diffusion bonding process.