Phase Field Modeling of the Microstructure Evolution in a Steel Workpiece under High Temperature Gradients

Abstract

Electrical discharge machining (EDM) is an ablative process with main thermal active principle. The applied thermal energy during this process leads to microstructure modifications in the rim zone of the eroded workpiece. These induced microstructure modifications directly affect the functionality of the workpiece. Nevertheless, these modifications cannot be easily predicted. Therefore, finding new methods for prediction of these modifications is of great interest both in academia and in industry.The microstructure modifications in the rim zone of an eroded workpiece are partly results of liquid-solid phase transformations in the recast layer and solid-solid phase transformations in the heat affected zone (HAZ). Therefore, by simulation of the microstructure evolution in these regions, their final microstructure can be predicted. Despite of the recent advances in the material simulation science, only few studies on simulation of microstructure evolution during EDM can be found in literature. This can be explained by the high temperature and temperature gradients that act during this process. These extreme boundary conditions evoke different complexities during material simulations.In this work, the complexities, which appear during the simulation of microstructure evolution for EDM are addressed. Furthermore, a simulation model for description of the microstructure evolution in a steel material under high temperature gradients is developed. The developed model is based on the phase field approach. Due to the potentials of this mathematical approach in describing the kinematics of multiphase systems, it became an attractive method for simulation of microstructure evolution. Although, the implemented temperature gradients are lower than the actual values, this model can be later used for simulation of the microstructure evolution in the HAZ of an eroded workpiece.