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M: Metallphysik

M 5: Symposium: Phasenumwandlungen in Schmelzen III

M 5.4: Vortrag

Montag, 24. März 2003, 15:30–15:45, IFW A

Phase-field simulations of solidification using a finite element method with an adaptive mesh refinement — •Denis Danilov and Britta Nestler — University of Applied Sciences Karlsruhe

Phase-field approaches allow to describe solid-liquid phase transitions in a thermodynamically consistent way. The physical effects occuring during solidification such as heat and mass transfer in phases, the release of latent heat, solute trapping, the Gibbs-Thomson relation and interface attachment kinetics can be obtained on the basis of an entropy functional. Sharp interface limit allows to do a relationship between parameters of the phase-field model and material properties of alloys. From a computational point of view, the advantage of phase-field models consists in avoiding the explicit tracking of the interfaces. However it is required that the spatial resolution of the numerical method must be greater than the thickness of the diffusive solid-liquid transition layer. The interfacial thickness itself must be less than the characteristic scale of the growing microstructure. In this case, a nonuniform grid with adaptive refinement can dramatically reduce the use of computational resources against a uniform grid with the same spatial resolution. For numerically solving the set of evolution equations, a finite element method with a semi-implicit time discretization was used. The grid refinement criterion is based on values of the phase-field, the concentration and the temperature gradients. Dendritic growth into an undercooled melt as well as the subsequent heating and remelting of dendrites were investigated and compared with experimental observations. Also simulations of multiphase solidification phenomena (eutectic growth) were carried out.