Recovery and recrystallization in the superplastic deformation of AA5182

The coarse-grained Al alloy AA5182 exhibits poor superplasticity with a maximum elongation to failure not exceeding 220% at 450 degrees C and at 10(-2) s(-1). The low values of the strain rate sensitivity indicate that the dislocation velocity is quite high and necking is developed quite soon during extension. The size (often exceeding 1 mu m) and the distribution of the precipitates render them incapable of pinning the subgrain boundaries efficiently. As a result recovery and reconstruction by grain refinement occurs only within the necking region where the applied stress is concentrated. A fabrication method which will be able to introduce a large number of submicron sized precipitates will most likely result in sufficient pinning of the subgrain boundaries. This will promote recovery and reconstruction to take place more uniformly in the material rendering it appreciably superplastic.