5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Due to the significant effects of the underlying microstructure on the material properties, accurate understanding of microstructure evolution in solidification processes has attracted lots of attentions in recent years. The low melting point of the ternary eutectic Bi-In-Sn alloy has lead to accurate in situ observations of its solidification process in experimental studies. Although these observations have deepened our understanding of microstructure evolution, due to complexity of the procedure there are lots of open questions of ongoing mechanisms. In the current study a thermodynamically consistent phase-field model based on the Grand potential approach is utilized to simulate the pattern formation in directional solidification of the system. As the first step of simulation studies, CALPHAD database is benefited to model the Gibbs energies and derive the chemical potentials of associated phases and the driving forces of the solidification process. Based on the reported system and process parameters like interfacial energies, solidification velocities and temperature gradient, two and three dimensional simulations are performed. The experimentally investigated 2D lamellar microstructure with ABCB repeat unit (A: $\gamma$-Sn , B: BiIn$_2$ , C: $\beta$-In) is achieved and the effects of material and simulation parameters on the phase arrangement is studied. Case studies of different instabilities like oscillations of phases boundaries, bifurcation and tilting of solidified phases are performed to investigate their stability ranges. The anisotropy of interfacial energies is considered as an effective parameter in pattern formation which is difficult to be controlled or measured in experimental studies. By means of different anisotropy models and the possibility of exact control of parameters,the effects of orientation and strength of the exposed anisotropy is determined. These effects can be summarized as changes in repeat unit and strength of the observed instabilities. Finally for each solidification velocity, the most stable conditions are introduced.