Deformation behavior of hot-rolled IN718 superalloy under plane strain compression at elevated temperature

The hot deformation behavior of hot-rolled IN718 superalloy was studied by plane strain compression in the temperature range of 900-1050°C and strain rate range of 10^-3-10s^-1. The results showed that the flow curves exhibit weak softening at most deformation conditions. However, intense softening caused by adiabatic heating was observed in the flow curves when the alloy was deformed at high strain rate (10s^-1), and these curves are characterized by unique "double-peak" which cannot be observed in those under uniaxial compression. Intensive strain localization and dynamic recrystallization occurred in the deformed specimens. Constitutive model based on the hyperbolic-sine equation was established to characterize the dependence of flow stress on strain, strain rate and temperature, and the activation energy was estimated to be 429kJ/mol. The processing maps were constructed to evaluate the power dissipation efficiency (η) and recognize the instability regimes. Optimum parameters were obtained in the temperature range of 1030-1050°C at strain rates of 0.02-0.1s^-1 for plane strain compression.