Three-Dimensional Analysis of Microstructure Formation and the Effect of Solidification Velocity in Columnar Dendritic Growth of Succinonitrile-Based Model Alloys

During the solidification of molten steel, the progression of columnar dendrite growth significantly influences the final microstructure through its morphology and microsegregation behavior. Consequently, comprehending and controlling the formation process of the solidification structure is essential for minimizing casting defects. In this study, we explored the three-dimensional morphology of columnar dendrites and the solute concentration distribution in the liquid phase by employing fluorescence imaging of a ternary solution model material. The solution comprised succinonitrile as the solvent, with water and the fluorescent reagent Lumogen R Yellow 083 (LY) as solutes. We also investigated the impact of solidification rate on columnar dendrite growth. Utilizing a confocal system, we acquired the three-dimensional structure near the dendrite tips, identified its characteristics, and assessed the fraction of solid based on the captured images. Furthermore, by examining the solidification morphology across a range of solidification rates from 0.010 to 0.500 mm s−1, we observed variations in primary arm spacing and the transition from aligned dendrites to superdendrites, determining that each solidification morphology could be explained by the corresponding solidification conditions. Additionally, by evaluating the LY concentration between primary arms at various heights from the primary dendrite axis and distances from the dendrite tip, we demonstrated that it could generally be reproduced by relatively simple solidification models.