Constitutive relationship and hot deformation behavior of Armco-type pure iron for a wide range of temperature

The hot deformation behavior and constitutive relationship of Armco-type pure iron were investigated using isothermal compression tests with a wide range of temperature and strain rate ranging from 923 to 1523 K, and 0.1 to 10 s(-1), respectively. When deformed with a single phase, the flow stress of Armco- type pure iron increases accompanied by the increase of strain rate and the decrease of deformation temperature. Instability phenomenon of Armco-type pure iron appears when deformed with dual phase. gamma-Fe undergoes completed discontinuous dynamic recrystallization (dDRX) at all hot deformation conditions. alpha-Fe undergoes uncompleted dDRX process at high temperature and low strain rate, however, dynamic recovery (DRV) process is the main restoration process for a-Fe at low temperature and high strain rate. The modified Arrhenius-type constitutive equation considering strain compensation is used to describe the flow stress of gamma-Fe and alpha-Fe. From correlation coefficient (R), root mean square error (RMSE) and average absolute relative error (AARE), the predictability of the constitutive equation for the two phases of Armco-type pure iron was evaluated. (C) 2014 Elsevier Ltd. All rights reserved.