Understanding hot workability and flow stress prediction through processing map with microstructural correlation for HY85 steel

Abstract

In this study, the hot compression tests of HY85 steel have been experimented by using thermomechanical simulator Gleeble 3800 in hot compression temperature range of 750°C-1,100°C under strain rates between 0.001-10 s-1 up to true strain 0.7. It is worth noticing from the results that the flow stresses are dependent on the combination of temperature and strain rate. Adiabatic heating corrections of experimental flow stress data were carried out and were used to model stress-strain curves. The predictability of these stress-strain curves was confirmed from experimental results. True stress-true strain curves show the peak stresses followed by softening probability because of the existence of dynamic recrystallization (DRX). The apparent activation energy is calculated to be 360 KJ/mol using the sinh type constitutive equation, and it is observed that its value decreases with increasing strain. Hot compression of HY85 steel is controlled by dislocation climb and glide (n = 6.3). The processing maps are plotted based on different dynamic materials modeled with strain rate versus temperatures. The flow localization is one of the primary factors with resulting instability, which is revealed from the microstructure. Moreover, the partial DRX was noticed besides the grain boundaries and compression bands. Workability regions were identified using processing maps in the domain of strain rate and temperature and verified with microstructures. Copyright © 2019 by ASTM International.