Numerical prediction of austenite grain size in a bar rolling process using an evolution model based on a hot compression test

A microstructure evolution model was formulated by characterizing the kinetics of static (SRX) and metadynamic (MDRX) recrystallization in consideration of the experimental data using single and double compression tests of AISI 4135 at various temperatures and strain rates. The evolution model consisted of equations for SRX, MDRX, and grain growth was implemented into an in-house finite element program to simulate the process. Numerical prediction of austenite grain size (AGS) evolution during a hot bar rolling of AISI 4135 was conducted and presented. The predicted results were compared with the experimental data obtained from the hot bar rolling and the numerical results based on other AGS models available in the literature which were derived based on torsion tests. The present model determined in the current investigation based on compression tests shows better agreement with the experimental data than the earlier works. The critical strains determined from compression tests were relatively smaller than those from the torsion tests, which influenced the overall recrystallization and grain growth behaviors. Also, the current model was beneficial to understand the effect of recrystallization behavior and control the microstructure evolution during hot bar rolling.