Microstructure Analysis and Segmented Constitutive Model for Ni-Cr-Co-Based Superalloy during Hot Deformation

Abstract

In a thermal simulator of Gleeble-3500, isothermal hot compression tests were performed on a Ni-Cr-Co-based superalloy at deformation temperatures ranging from 1323 K to 1423 K and with strain rates of 0.01, 0.1, 1, and 5 s−1. We obtained the true stress–strain curves, and the microstructures of deformed samples were analyzed by electron backscatter diffraction (EBSD) technique. The segmented constitutive models were developed to predict the flow stress, and the dynamic recrystallization grain size model was established to evaluate the microstructure evolution for a Ni-Cr-Co-based superalloy. It is found that discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) appear simultaneously in the Ni-Cr-Co-based superalloy during hot deformation, with the latter not being active. Comparison between the experimental and predicted results indicates that the proposed models can describe and interpret the work-hardening and dynamic softening behaviors as well as the evolution characteristic of dynamic recrystallization grain size of the Ni-Cr-Co-based superalloy. In the error analysis of the segmented constitutive models, correlation coefficient (R) is 0.988 and average absolute relative error (AARE) is 6.94%, and for the AGS of DRX, R is 0.974 and AARE is 5.83%, which both have good accuracy.