Events
Time: 5:55 p.m.
Place: CALPHAD XLI 2012, Berkeley, USA
Lijun Zhang, State Key Laboratory of Powder Metallurgy, Central South University, Changsha, China
Ingo Steinbach
In rapid phase transformations, interfaces are often driven far from equilibrium, and the chemical potential may exhibit a jump across the interface. In order to treat such situations, a phase-field model for heterogeneous systems, which can be described by separate concentration fields in all phases, has been extended to treat situations with a potential jump between the phases [1]. The key new feature of this new model is that the two concentration fields are linked by a kinetic equation which describes exchange of the components between the phases, instead of the equilibrium partitioning condition [2-6]. The associated rate constant influences the interface dissipation. For rapid exchange between the phases, the chemical potentials are equal in both co-existing phases at the interface as in previous models [5,6], whereas in the opposite limit strong non-equilibrium behaviour can be modelled. This is illustrated by simulations of a diffusion couple and of solute trapping during rapid solidification.
This new phase-field model was then generalized to a multi-component multi-phase one [7] in the framework of the multi-phase-field formalism [8], allowing the description of multiple junctions with arbitrary number of phases and components. The model demonstrates the decomposition of the nonlinear interactions between different phases into pairwise interaction of phases in multiple junctions. Besides, the direct coupling to the real CALPHAD thermodynamic and atomic mobility databases was shown for quantitative phase-field simulations. The present models were also successfully applied to simulate the eutectic and peritectic growth in some real alloys.
References [1] Steinbach I, Zhang L, Plapp M. Acta Mater 2012;accepted for publication. [2] Tiaden J, Nestler B, Diepers HJ, Steinbach I. Physica D 1998;115:73. [3] Kim SG, Kim WT, Suzuki T. Phys Rev E 1999;60:7186. [4] Karma A. Phys Rev Lett 2001;87:11571. [5] Kim SG, Kim WT, Suzuki T. Phys Rev E 1999;60:7186. [6] Eiken J, Böttger B, Steinbach I. Phys Rev E 2006;73:066122. [7] Zhang L, Steinbach I. Acta Mater 2012;in revision. [8] Steinbach I. Mod Sim Mat Sci Eng 2009;17:073001.
