Growing demands for sustainability and energy efficiency require continuous material optimization. Thus, simulation is also increasingly applied in the area of forming technology and heat treatment. There is still a high potential in improving simulation results to represent forming processes realistically with the help of a sound microstructure simulation.
The recrystallization models in MatILDa®
The semi-empirical recrystallization model (also called grain size model or microstructure model) integrated in MatILDa® allows to calculate microstructure changes due to the recrystallization processes during hot forming - as well as the determination of the average grain size including the hardening and softening behavior and grain growth.
During forming, in metallic materials recrystallize dynamically as soon as the critical true strain for the start of dynamic recrystallization has been exceeded. Between two forming steps, the material can recrystallize statically, insofar as no dynamic recrystallization has taken place. Accordingly, dynamic and static recrystallization are the most important processes involved in this kind of calculation. Here, MatILDa® determines the associated recrystallized fractions as well as the grain sizes of the newly formed grains. The average grain size is then calculated based on the grain sizes of the recrystallized and non-recrystallized portions. Forming-induced recrystallization processes are terminated by the start of phase transformation. After completion of the recrystallization process, grain growth processes start above the recrystallization temperature (approx. 0.75 * melting temperature) of the material. The latter are also taken into account in the grain size calculation.
Validity ranges of the recrystallization models
Also, for the recrystallisation model, the validity ranges are decisive for their application in a simulation project. That is why the validity ranges are displayed in the respective model in MatILDa®. The semi-empirical approaches are based on Sellars and Whiteman.
Progress starts at micro level
The equations of the semi-empirical model can be displayed in the recrystallization model in MatILDa®. The coefficients can be adapted individually by the user. Furthermore, we are happy to support in the acquisition and the parametrization of a new recrystallization model.
The recrystallization model is available for a wide range of steel alloys and Ni-based alloys.