Flow behavior and constitutive model for Ni-20.0Cr-2.5Ti-1.5Nb-1.0Al superalloy compressed below γ′-transus temperature

Hot deformation behavior of Ni-20.0Cr-2.5Ti-1.5Nb-1.0Al superalloy has been investigated at the temperatures of 940-1060 degrees C (all below nominal gamma'-transus temperature of 1080 degrees C) and strain rates of 0.001-1.0 s(-1). The results show that true stress-true strain curves exhibit a peak stress at a small strain, after which the flow stress decreases monotonically until high strains, showing a dynamic flow softening. The flow stress consists of four different stages, viz., work-hardening, stable, softening and steady stage. Flow stress decreases with increasing temperature and decreasing strain rate. The constitutive equation represented as a function of temperature, strain rate and true strain was developed, which gives an accurate and precise estimate of flow stress. Hot deformation should be carried out under condition of (T-opi: 1020 degrees C, (epsilon) over dot(opi) : 1.0 s(-1)) obtain fine homogeneous microstructure. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.