Equal-strength precision diffusion bonding of AA6063 aluminum alloy with the surface passivated by a self-assembled monolayer

Precision diffusion bonding of aluminum alloy requires good mechanical properties and very low deformation. However, oxidation lowers the quality of the joint. This paper used a self-assembled monolayer, 1-hexyl mercaptan, on the aluminum surface to prevent the secondary oxidation after pre-bonding treatment. An AA6063/Ni/AA6063 sandwich structure joint was intentionally designed and bonded to characterize the effect of the self-assembled monolayer. AA6063/AA6063 joints were diffusion bonded, in which three different pre-bonding surface treatments were used that were as-cleaned, ethanol adsorbed and self-assembled monolayer passivated. With the surface passivated by selfassembled monolayer, there were few voids at the bonding interface. Ductile fracture was observed during tensile testing. The joint had a bond ratio of 97.4% and elongation of 20.4%, which is very close to the base metal and is considered as equal-strength bonding.