New constitutive model and hot processing map for A100 steel based on high-temperature flow behavior.

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Understanding the hot processing behavior of advanced steels like A100 is critical for optimizing manufacturing processes.
• Accurate constitutive models are essential for predicting material flow and microstructural evolution during thermomechanical treatments.

Purpose of the Study:

• To develop a predictive constitutive model for A100 steel's flow behavior.
• To establish a hot processing map to identify optimal processing windows for A100 steel.
• To correlate processing parameters with dynamic recrystallization and resulting microstructure.

Main Methods:

• Isothermal compression tests were conducted at temperatures from 1073 to 1353 K and strain rates from 0.01 to 10 s⁻¹.
• True stress-strain data were used to establish a constitutive model and a hot processing map.
• Analysis focused on energy dissipation rate and its relation to dynamic recrystallization.

Main Results:

• A constitutive model with a correlation coefficient of 0.9913 accurately predicts A100 steel's flow behavior.
• Dynamic recrystallization, leading to a uniform equiaxed grain structure, occurs when the energy dissipation rate exceeds 25%.
• Unstable processing regions (high strain rate, low temperature) result in coarse, elongated microstructures detrimental to mechanical properties.

Conclusions:

• The developed constitutive model provides excellent predictive capability for A100 steel flow behavior.
• The optimal hot forming window for A100 steel is identified as 1153-1353 K and 0.01-10 s⁻¹, promoting complete dynamic recrystallization.
• Avoiding unstable processing conditions is crucial for achieving desirable microstructures and mechanical properties in hot-formed A100 steel.