[SY-F2] Symposium F-2

[SY-F2] Phase-field simulations of coupled dendritic-eutectic growth

^○Marco Seiz¹, Michael Kellner^1,2, Johannes Hötzer^1,2, Philipp Steinmetz³, Britta Nestler^1,2 (1.Institute of Applied Materials - Computational Materials Science, Karlsruhe Institute of Techology, Germany, 2.Institute of Digital Materials Science, Karlsruhe University of Applied Sciences, Germany, 3.Department of Materials Science and Engineering, University of Alabama at Birmingham, United States of America)

The solidification of alloys shows a large variety of different microstructures depending on the material system and processing conditions. Since material properties such as tensile strength are dependent on the microstructure, its prediction is a topic of high interest in order to produce materials with tailored properties. Whereas theory is capable of investigating simple geometries, simulations are necessary in order to ascertain the influence of complex evolving geometries. An example of this is the coupled growth of dendrites and eutectics, which typically grow at different length scales.

One way to simulate such problems is the phase-field method which has been established as a versatile tool to investigate microstructural evolution. The used phase-field model is based on a grand potential approach with parabolic free energies approximating thermodynamic CALPHAD data of the system Al-Cu. Additionally, an ad-hoc nucleation mechanism is implemented.

Validation is done by comparison to analytical theories of pure dendritic and eutectic growth. Following the validation, the coupled growth of coarse dendrites and fine eutectics during directional solidification is investigated in two as well as three dimensions. Depending on the process parameters, observations include closely-spaced dendrites turning into cells, stable coupled growth of dendrites and eutectics, nucleation of eutectic on dendritic sidebranches as well as transitions to a completely eutectic state. Based on these results a tentative microstructure map is established.