Activation Energy for Superplastic Flow Above Critical Temperature of Die Steels

Some commercial cold working die steels GCr15 and CrWMn with ultra-fine grain size were chosen as tested materials to research the activation energy for superplastic flow at different temperatures and strain rates above critical temperature. Based on the Arrhenius equation, the activation energy for superplastic flow is evaluated. The activation energy at constant strain rate is estimated by the logσt vs 1/T relationship. The results show that the activation energy is usually small under the conditions of optimal flow. The characteristics of superplastic deformation of steels above the critical temperature were also analyzed.