Microstructure and Constitutive Equation of Hot Compressive Fe-15Mn-15Al-5Ni-1C Low-Density Steel

Area of Science:

• Materials Science
• Metallurgy
• Physical Metallurgy

Background:

• Investigating the hot deformation behavior of advanced high-strength steels is crucial for optimizing manufacturing processes.
• Understanding dynamic recrystallization (DRX) is key to controlling microstructure and mechanical properties during hot working.
• Fe-15Mn-15Al-5Ni-1C low-density steel presents unique characteristics due to its complex composition.

Purpose of the Study:

• To investigate the hot deformation behavior and dynamic recrystallization (DRX) of as-cast Fe-15Mn-15Al-5Ni-1C low-density steel.
• To establish a constitutive equation and a critical DRX model for this specific steel alloy.
• To elucidate the influence of temperature and strain rate on the deformation mechanisms and DRX kinetics.

Main Methods:

• Hot compression experiments were conducted across a temperature range of 925–1150 °C and strain rates from 0.01 to 10 s^-1.
• Analysis of work hardening, softening, and steady-state flow behavior under varying hot working conditions.
• Construction of a constitutive model and a critical DRX model based on experimental data.

Main Results:

• Higher strain rates induced significant work hardening and rapid softening, whereas lower strain rates promoted steady-state flow.
• The activation energy for deformation was determined as 540 kJ/mol, with a stress index of 4, indicating solute dragging and dislocation climbing as dominant mechanisms.
• Increased deformation temperature and strain rate reduced the critical stress for DRX, facilitating the recrystallization of austenite and δ-ferrite phases.

Conclusions:

• The hot deformation of Fe-15Mn-15Al-5Ni-1C steel is governed by strain rate-dependent mechanisms, including solute dragging and dislocation climbing.
• Dynamic recrystallization is influenced by temperature and strain rate, with critical stress decreasing under more severe conditions.
• The resulting microstructure after hot compression comprises austenite, ferrite, and κ-carbide phases, highlighting the complex phase evolution during processing.