A Physically Based Mean Field Model for Strain‐Induced Precipitation and Recrystallization in High‐Strength Low‐Alloy Steels

A physically based mean field model developed to predict the microstructural evolution during the thermomechanical control process of X70 high‐strength low‐alloy (HSLA) steels is presented. The physically based mean field model incorporates a new integrated precipitation and recrystallization model developed to describe the interaction between strain‐induced precipitation of niobium and titanium carbonitrides and static recrystallization of austenite. The integrated model considers an effective Zener pinning force for the multimodal particle size distribution (PSD) of precipitates, an effective grain‐boundary mobility for the solute drag effect of niobium, and an inhomogeneous stored energy for austenite recrystallization. Given a processing route, the model predicts the variation of austenite grain size, recrystallized and precipitated fractions, and evolution of PSDs of precipitates. Model predictions reveal an excellent agreement with experimental grain size measurements and a final average ferrite grain size of 3.81 μm is achieved. The proposed model considers the heterogeneous nature of recrystallization and precipitation and can contribute to the process design of the HSLA and microalloyed steels.