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)

Formation process of equiaxed structure is quite complicated phenomenon. The most difficult point in the modeling of the equiaxed structure formation process would be a motion of dendrites. In our previous study, we succeeded in expressing the growth of a single dendrite accompanying the motion by coupling phase-field method, lattice Boltzmann method, and equations of motion [R. Rojas, T. Takaki, M. Ohno, J. Comp. Phys. 298 (2015) 29-40]. After that, we have extended the model to the polycrystalline solidification, where we expressed the multiple dendrite growth with motion, collision, and coalescence and subsequent grain growth occurred after the formation of grain boundaries [T. Takaki, R. Sato, R. Rojas, M. Ohno, Y. Shibuta, Comp. Mater. Sci. 147 (2018) 124–131]. In the model, we assumed the same energy and mobility for all solid-liquid interfaces and grain boundaries. In this study, we improve the accuracy of our previous polycrystalline solidification model by employing a multi-phase-field model [I. Steinbach, F. Pezzolla, Physica D 134 (1999) 385-393], and accelerate the simulation by employing the APT (active parameter tracking) algorism for multiple phase-field variables and the multi-GPU (graphical processing unit) parallel computation. Finally, we introduce some simulation examples, such as the formation processes of the sediment bed [C. Beckermann, C.Y. Wang, Metal. Mater. Trans. A 27 (1996) 2784-2795] and the equiaxed structure through dendrite fragmentation [L. Arnberg, R.H. Mathiesen, JOM 59 (2007) 20-26].