Influence of strain rates and strain states on the formability of a superplastic 8090 aluminum alloy

A series of experiments were performed using various strain rates and strain states during the superplastic deformation of a fine-grained 8090 aluminum alloy. Rectangular pans, and hemispherical and cylindrical capped parts were deformed superplastically to study the effects of forming paths and strain states on the nucleation and growth characteristics of cavities. The results showed that the cavity fraction decreased with decreasing strain rate due to a lower rate of cavity nucleation at a lower strain rate. The strain states did have an effect on the cavity fraction in the formed parts. The cavitation level was lower in parts formed equi-biaxially. A two-step strain rate deformation could reduce the cavitation in the formed part.