Activation energy for superplastic deformation of IN718 superalloy

The strain rate sensitivity index (m) and activation energy (Q) parameters of the constitutive relationship for superplastic deformation of the IN718 superalloy were evaluated after prestraining. The flow behavior of IN718 superalloy over the strain rate range of approximately 1×10-5×10-4 s-1 and the temperature range of 1173-1248 K were examined. The log(σ)-log(ε) plot delineated the predominantly superplastic region over the entire temperature range, with m increasing from 0.37 at 1173 K to 0.58 at 1248 J. The Arrhenius plot revealed two activation energy values for superplastic deformation at a transition temperature of 1218 K.