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

• Hot deformation behavior of Armco-type pure iron has been analyzed.
• γ-Fe and α-Fe undergo completed dDRX and uncompleted dDRX, respectively.
• Sharp increase in peak stress appears as long as α-Fe changes to γ-Fe.
• Modified constitutive equation is used to predict the flow stress of γ-Fe and α-Fe.
• Predictability of the constitutive equation is evaluated in terms of the R, RSME, and AARE.

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. γ-Fe undergoes completed discontinuous dynamic recrystallization (dDRX) at all hot deformation conditions. α-Fe undergoes uncompleted dDRX process at high temperature and low strain rate, however, dynamic recovery (DRV) process is the main restoration process for α-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 γ-Fe and α-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.