Dynamic recrystallization behavior and microstructure evolution of low-density high-strength Fe–Mn–Al–C steel

Abstract

The hot deformation behavior of low-density high-strength Fe–Mn–Al–C steel at T = 900–1150 °C and ε˙ = 0.01–10 s−1 is studied using the Gleeble-3500 thermo-mechanical simulator. The rheological stress curve characteristics of the steel are analyzed through experimental data and the dynamic recrystallization activation energy is calculated. The critical strain/stress, peak strain/stress and steady-state strain/stress models of dynamic recrystallization are characterized by introducing the dimensionless parameter Zener-Hollomon. The microstructure evolution is analyzed and the dynamic recrystallization state diagram of the steel is drawn. The results indicated that the steel is a negative temperature-sensitive and a positive strain rate-sensitive material. The dynamic recrystallization activation energy is 669.844 kJ mol−1. With the decrease of ε˙ or the increase of T, the Z parameter decreases gradually and the dynamic recrystallization behavior is more likely to occur; however, its grain size increases accordingly. The fine and uniform grain structure can be obtained by hot working in the range of 950–1000 °C/0.01–0.1 s−1 and 1050–1100 °C/1–10 s−1. Finally, the prediction model for the dynamic recrystallization average grain size is established, and the correlation coefficient (R) of the prediction model is 0.996; therefore, the model has a high prediction accuracy.

Keywords

• Low-density high-strength steel
• Microstructure evolution
• Dynamic recrystallization state diagram
• Hot deformation
• Grain size