An Internal-State-Variable-Based Continuous Dynamic Recrystallization Model for Thermally Deformed TC18 Alloy

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Continuous dynamic recrystallization (CDRX) significantly impacts alloy microstructure during hot forming.
• TC18 alloy, with moderate to high stacking fault energy, exhibits complex microstructural evolution under deformation.

Purpose of the Study:

• To investigate the flow stress and CDRX behavior of TC18 alloy during hot deformation.
• To develop and validate an internal state variable (ISV)-based CDRX model.

Main Methods:

• Hot deformation experiments on TC18 alloy.
• Microstructural analysis focusing on grain boundary evolution (LAGBs to HAGBs).
• Development of an ISV-based CDRX model incorporating dislocation density, temperature, and misorientation.

Main Results:

• Deformation induced new low-angle grain boundaries (LAGBs) that transitioned to high-angle grain boundaries (HAGBs).
• The ISV-based model showed high accuracy (R=0.989, RAAE=6.69%, RMSE=4.78 MPa) in predicting true stress.
• Model accurately predicted decreased grain size with higher strain rates and lower temperatures, indicating a shift to a continuously recrystallized substructure.

Conclusions:

• The developed ISV-based model effectively captures CDRX phenomena in TC18 alloy.
• Microstructure transitions from coarse-grained to a finer, continuously recrystallized substructure under specific processing conditions.
• The model provides a quantitative tool for predicting microstructure evolution during hot forming.