Abstract
An effort has been made to establish a relation between Zener–Hollomon parameter, flow stress and dynamic recrystallization (DRX). In this context, the plastic flow behavior of Ti + Nb stabilized interstitial free (IF) steel was investigated in a temperature range of 650–1100 °C and at constant true strain rates in the range 10−3–10 s−1, to a total true strain of 0.7. The flow stress curves can be categorized into two distinct types, i.e. with/without the presence of steady-state flow following peak stress behavior. A novel constitutive model comprising the strain effect on the activation energy of DRX and other material constants has been established to predict the constitutive flow behavior of the IF steel in both α and γ phase regions, separately. Predicted flow stress seems to correlate well with the experimental data both in γ and α phase regions with a high correlation coefficient (0.982 and 0.936, respectively) and low average absolute relative error (7 and 11%, respectively) showing excellent fitting. A detailed analysis of the flow stress, activation energy of DRX and stress exponent in accord with the modelled equations suggests that dislocation glide controlled by dislocation climb is the dominant mechanism for the DRX, as confirmed by the transmission electron microscopy analysis.Graphic
Highlights
Interstitial Free steel (IF) steel is often termed as a clean steel that refers to very low to negligible level of interstitial solute atoms that may be present in the steel and the Fe lattice is practically free of strains caused by the interstitials, resulting in high formability and high strain rate sensitivity
The dilation versus temperature curve acquired from the dilatometry test and the stress versus temperature curve generated from the continuous cooling compression (CCC) test for the IF steel are shown in Fig. 2a, b, respectively
The hot/warm deformation tests were performed on an IF steel within the temperature range of 650–1100 °C and at different strain rates in the range 1 0−3 to 10 s−1
Summary
Interstitial Free steel (IF) steel is often termed as a clean steel that refers to very low to negligible level of interstitial solute atoms that may be present in the steel and the Fe lattice is practically free of strains caused by the interstitials, resulting in high formability and high strain rate sensitivity. Takaki et al [13] proposed a relation between the initial microstructure and mechanical behavior of the materials through a multi-phase field, FES-DRX model considering the DRX kinetics Using this model, they could estimate the macroscopic mechanical behavior during hot-working and the predictions matched well the experimentally obtained results. Puchi-Cabrera et al [15] performed a hot working simulation study on a C–Mn steel using Sellars-Tegart-Garofalo model and derived an innovative constitutive equation in differential form These approaches were found to be beneficial to represent the evolution of flow stress under variable temperature and strain rate conditions. The reliability of the constitutive equations for different phases developed in the present study, have been validated through determining the values of correlation coefficients (Rcc) and average absolute relative errors (AARE)
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