Hot deformation behavior and constitutive modeling of fine grained Inconel 718 superalloy

Highlights: • Hot deformation behavior of fine grained Inconel 718 superalloy was investigated. • Flow behavior was predict by a strain-compensated Arrhenius type constitutive equation. • Processing map was used to predict flow instability and optimize process parameters. • The optimum processing parameter were determined to be 1100 °C and 0.1 s⁻¹. The hot deformation behavior of fine grained Inconel 718 superalloy was investigated by compression test in the temperature range of 950 to 1150 °C and strain rate range of 0.1–10 s⁻¹. At low temperatures and high strain rates, the flow stress rapidly increased to a peak value with increasing strain at the initial stage of deformation. After attaining peak stress, the flow curves exhibited an obvious phenomenon of flow softening. At high temperatures and low strain rates, the flow curves exhibited typical characteristics of dynamic recrystallization. A strain-compensated Arrhenius type constitutive equation was used to predict the flow behavior of the alloy. The relationship between the material constants (i.e. α, Q, n and lnA) in Arrhenius-type constitutive equation and true strain was established by a fifth order polynomial. The flow stress values predicted by the developed constitutive equations were in good agreement with the experimental values, showing that the developed constitutive equation can give a precise estimate for the flow stress during hot deformation. The processing maps of fine grained Inconel 718 superalloy for hot working at different strains were constructed. The optimum processing parameters were determined to be the deformation temperature of 1100 °C and strain rate of 0.1 s⁻¹.