Control of cavitation during superplastic forming of high strength aluminium alloys

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Abstract
This investigation deals with superplastic deformation and cavitation behaviour of a 7475 high strength aluminium alloy in uniaxial tension. Intergranular cavitation increases sharply with strain as a result of continuous nucleation, thus limiting the ductility to relatively small strains in the superplastic range and affecting the room temperature service properties. To reduce the overall cavitation, several processes have been carried out. They involve treatments of the material with or without superimposed hydrostatic pressure and they can be applied before, during, or after deformation. The results of these processes are presented and compared. It is concluded that cavitation can be significantly reduced and even eliminated. Such a result can increase the use of superplastic forming for industrial applications in aeronautics and aerospace technology. MST/985