The deformation behaviour of a dispersion strengthened superplastic zinc alloy

The deformation behaviour of a new dispersion strengthened superplastic zinc alloy was investigated. A significant long range internal stress was observed at all strain-rates. The activation volume of deformation decreased very rapidly with a decrease in the true effective stress. The maximum strain-rate sensitivity corresponds to a region of change from this high stress dependence of the activation volume to a much lower stress dependence. The observation of a metallographic halo effect shows that apart from dislocation movement, diffusive creep plays a role during superplastic deformation. It is stipulated that both these processes aid boundary sliding which accounts for the largest part of the strain.