INTERACTIONS BETWEEN COLUMNAR SOLIDIFICATION AND SEGREGATION: A COMPARISON OF THE PREDICTIONS OF A CAFE MODEL WITH IN-SITU OBSERVATIONS

摘要

A two-dimensional (2D) cellular automaton (CA) - finite element (FE) model has been extended to simulate the solidification of binary alloys while accounting for macrosegregation. The solidification experiment of a gallium - 5 wt% indium alloy developed by Yin and Koster provides a good benchmark for comparison with predictions of the model. Observed and simulated time evolutions of the development of the grain structure and the macrosegregation can be directly compared, together with mesosegregation such as segregated channels. These channels differ from freckle-type segregation described in the literature. They form as a result of the dynamics of the columnar growth front and its interaction with the fluid and solute flows. Comparisons of the predictions of the CAFE model with a purely macroscopic FE model also reveal the influence of accounting for the growth undercooling in numerical modeling of solidification.