Hot Deformation and Dynamic Recrystallization Behavior of Austenite-Based Low-Density Fe-Mn-Al-C Steel

doi:10.1007/s40195-016-0406-1

Abstract

Abstract:

The hot deformation and dynamic recrystallization (DRX) behavior of austenite-based Fe-27Mn-11.5Al-0.95C steel with a density of 6.55 g cm^-3 were investigated by compressive deformation at the temperature range of 900-1150 °C and strain rate of 0.01-10 s^-1. Typical DRX behavior was observed under chosen deformation conditions and yield-point-elongation-like effect caused by DRX of δ-ferrite. The flow stress characteristics were determined by DRX of the δ-ferrite at early stage and the austenite at later stage, respectively. On the basis of hyperbolic sine function and linear fitting, the calculated thermal activation energy for the experimental steel was 294.204 kJ mol^-1. The occurrence of DRX for both the austenite and the δ-ferrite was estimated and plotted by related Zener-Hollomon equations. A DRX kinetic model of the steel was established by flow stress and peak strain without considering dynamic recovery and δ-ferrite DRX. The effects of deformation temperature and strain rate on DRX volume fraction were discussed in detail. Increasing deformation temperature or strain rate contributes to DRX of both the austenite and the δ-ferrite, whereas a lower strain rate leads to the austenite grains growth and the δ-ferrite evolution, from banded to island-like structure.

Key words: Fe-Mn-Al-C steel, Hot deformation, Dynamic recrystallization, Yield-point-elongation-like effect

Ya-Ping Li, Ren-Bo Song, Er-Ding Wen, Fu-Qiang Yang. Hot Deformation and Dynamic Recrystallization Behavior of Austenite-Based Low-Density Fe-Mn-Al-C Steel[J]. Acta Metallurgica Sinica (English Letters), 2016, 29(5): 441-449.

Figures/Tables 11

Fig. 1 a Heat treatment and deformation processing, b optical microstructure of forged steel (the dark areas are austenite, and the white ones are the δ-ferrite)

Fig. 2 Flow stress-strain curves of the steel deformed at various temperatures and strain rates: a 0.01 s-1, b 0.1 s-1, c 1 s-1, d 10 s-1 (asterisk representing the yield-point-elongation-like effect)

Fig. 3 Optical microstructure a and TEM b of the sample deformed to the yield strain at 900 °C and 0.1 s-1

Fig. 4 Relationship between a \(\ln \dot{\varepsilon }\) and \(\ln [\sinh (\alpha \sigma_{\text{p}} )]\), b \(\ln [\sinh (\alpha \sigma_{\text{p}} )]\) and 1/T

Fig. 5 Relationship between \(\ln [\sinh (\alpha \sigma_{\text{p}} )]\) and ln Z

Fig. 6 θ-σ curves of the steel at various temperatures with strain rate of a 0.1 s-1, b 1 s-1

Fig. 7 Relationships between a ln σ p, ln σ c, ln σ y and ln Z, b ln ε p, ln ε c, ln ε y and ln Z

Fig. 8 Relationship between the \(\ln \ln \left( {1/\left( {1 - X} \right)} \right)\) and \(\ln ((\varepsilon - \varepsilon_{\text{p}} )/\varepsilon_{\text{p}} )\)

Fig. 9 Predicted results of DRX volume fraction under various deformation conditions: a 0.01 s-1, b 1150 °C

Fig. 10 Optical microstructures of the samples deformed under various conditions: a 900 °C, 1 s-1, b 1000 °C, 1 s-1, c 1100 °C, 1 s-1, d 1100 °C, 0.01 s-1, e 1100 °C, 0.1 s-1, f 1100 °C, 10 s-1 (The compression direction is vertical)

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