Microstructural evolution and constitutive equations of Inconel 718 alloy under quasi-static and quasi-dynamic conditions

The deformation behavior of IN718 superalloy was investigated using the hot compression tests in the temperature range of 950-1100 degrees C, and strain rates covering the quasi-static to the quasi-dynamic regions (0.001-10 s(-1)). The shape of flow curves as well as the corresponding work hardening rates analysis was utilized to reveal the dynamic recrystallization (DRX) phenomena. DRX was the dominant restoration mechanism in the whole temperature and strain rate domains, which was characterized by the optical and EBSD images. Extended flow softening was observed at high strain rates due to the adiabatic heating and dislocations interaction. In addition to the assessment the capability of Sellars equations, a new constitutive equation based on the multiple variable regression analysis was proposed for modeling the peak stress as a function of strain rate and temperature. Besides the simple form of the proposed model, it has a good accuracy for predicting the peak stress. (C) 2016 Elsevier Ltd. All rights reserved.