Modeling equiaxed solidification with melt convection and grain sedimentation-II. Model verification

A modified equiaxed solidification model was introduced in Part I. In Part II, a binary Al-Cu alloy casting is simulated using the aforementioned model. Important phenomena accompanying equiaxed solidification considered include: nucleation, globular grain growth, globular-to-dendritic transition, subsequent dendritic growth, recalescence, convection and grain transport. The influence of these events on the formation of the final microstructure (grain size, inter- and extradendritic eutectic) and macrosegregation is also examined. The first verification qualitatively reproduces the features of the previous models. The simulation results are quantitatively compared with the experiments of Nielsen and co-workers [Nielsen O, Appolaire B, Combeau H, Mo A. Metall Maier Trans 2001;32A:2049], and a satisfactory agreement is obtained. The new features of the current model and the uncertainty regarding the model assumptions and parameters are studied and discussed. The parameter studies indicate that the grain morphological parameters and the determination of diffusion lengths in different phase regions are the most critical/sensitive factors influencing the quantitative results, and demand further study. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.