1994 Volume 43 Issue 493 Pages 1304-1308
The effects of strain rate and strain on the structure of bonding interface and the behavior of surface oxide film during a superplastic forming and diffusion bonding processing have been investigated in the process of making laminates of 5083 aluminum alloy foils with conversion coating. It is likely that surface oxide films were broken at the intersections of grain boundary and foil surface, and that grains behind foil surface moved to the bonding interface by grain boundary sliding to contact with grains in the other foil which appeared at the bonding interface by the same way. To get a contact without any flaw between them, a certain surface pressure was required. At a strain rate of 6×10-4s-1, some flaws existed around oxide segments because of low flow stress, whereas at 2×10-2s-1, no flaw was found because of higher flow stress. In the case of large grain size caused by strain-induced grain growth observed at a low strain rate of 6×10-4s-1, the oxide segments were longer and waviness of the bonding interface was increased. It is noted that there were many oxide segments with double layers even after large deformation, which probably have low bonding strength.
