EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Evaluation of microstructural evolution is often essential for comprehension of aspects of locally occurring physicochemical based phenomena. Often this evaluation is restricted by external limitations such as high temperature phases and therefore impossible to put into execution or too complex to be performed excessively. Simulations have been used widely to model material behavior or properties in regions where a direct observation is impractical, but their extra- or interpolations are only as good as the assumptions they are based on. Those assumptions should be as few as possible for complexity reasons, but as many as necessary to reproduce the details you want to model in the first place. By "reverse engineering" the key aspects to obtain realistic grain size distribution over time and temperature, considering normal and abnormal grain growth have been found, with a discrete grain neighbor relationship to be the main inevitable parameter, to predict microstructural development in HSLA-steels. Annihilation, recovery and recrystallization during and after hat rolling has also been implemented considering subgrain formation and growth regarding additional driving forces such as dislocation density.
The validation of the grain growth model has been performed by taking control samples at different times and temperatures. Validation of the recrystallization kinetics has been done with double hit experiments with a Gleeble®. Since the high temperature austenitic phase was of interest, this information had to be extracted from the martensitic/bainitic microstructure at room temperature. Different approaches have been utilized to visualize and quantify the prior austenitic grains such as the Merengue2 software which performs the reconstruction based on EBSD measurements and etching primary grain boundaries with a modified picric acid solution.