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)

This second paper addresses the phase field modeling of columnar dendritic growth for different scenarios of fluid flow developing in response to gravitational forces. For this the experimental Ti-48Al-2Cr-2Nb alloy has been simplified to a binary alloy Ti-48 at.% Al. The 2D simulations confirm the decrease of the primary dendrite arm spacing with increasing gravity, nearly matching the experimental findings. In addition, the simulations show that above a critical magnitude of the gravity level dendrite tips display a characteristic splitting behavior, leading to highly branched microstructures. While tip-splitting can be periodic also without flow [1], the present results indicate that splitting events are closely coupled to the convection rolls between neighboring dendrites. The highly dynamic growth behavior however leads to an overall stable advancement of the average solidification front. The instabilities are discussed based on the imposed growth conditions and fluid flow velocities. The role of the anisotropy of the solid/liquid interface energy on the pattern dynamics will also be discussed. [1] Chen, Y., Billia, B., Li, D. Z., Nguyen-Thi, H., Xiao, N. M., & Bogno, A. A., Acta Mater. 66 (2014) 219-231