Effect of Solute Diffusion on Dendrite Growth in the Molten Pool of Al-Cu Alloy
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ES are the most common microstructures that can be observed in the solidification of metals and alloys. The properties of the final products are mainly influenced by the detail of dendrite morphology, micro-segregation pattern, and chemical characteristics. Solidification is known to be always accompanied by heat and solute transfer, which can thereby significantly influence the formation of solute segregation and dendritic patterns. In order to control the solidification structure and achieve the desired mechanical properties, fundamental knowledge about the mechanism of dendritic microstructure formation is needed to master. Many theoretical[1–4] and experimental[5–7] works have been carried out to characterize dendritic growth behavior. Young and Kerkwood[8] carried out a series of solidification experiments under steady-state conditions. Solute content at dendrite tips was analyzed. Primary and second arm spacings were measured. It was found that the primary arm spacing is related to the temperature gradient in the liquid GL and the growth velocity of the dendrite tips. Miyata et al.[9] proposed the linear relationships between tip radius and characteristics of dimensions of dendrites. The measured tip concentration was found in good agreement with theoretical predictions. However, due to the high temperature and
XIAOHONG ZHAN, CHENG GU, YUN LIU, and YANHONG WEI are with the College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China. Contact e-mail: [email protected] Manuscript submitted January 10, 2017.
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the rapid solidification process, it is difficult to observe the dendrite growth in the molten pool by experimental technology directly, and further research would be necessary. Numerous efforts have so far been devoted to characterize dendrite growth behavior using numerical models, such as phase field (PF) method,[10–14] front tracking (FT) method,[15–17] level set method,[18,19] cellular automaton (CA) method,[20–24] and so on. In Cortie’s study,[25] the solidification of a hypothetical liquid was studied. The model presented exhibits a change in microstructure as a function of thermal gradient. It was reported in Gandin’s paper[26] that the cell grid was superimposed to a coarser finite element mesh used for the solution of the heat flow equation. The potentiality of the CA–FE model was demonstrated. Beltran-Sanchez and Stefanescu[27] established a CA model which does not use an analytical solution to determine the velocity of the S/L interface as is common in other models, but solves the solute conservation equation subjected to the boundary conditions at the interface. Zaeem et al.[28,29] compared a CA–FE model and a PF FE model to simulate equiaxed dendritic growth during the solidification of cubic crystals. The simulation results from both models showed good agreement with the analytical LGK model in the tip growth velocity and the tip equilibrium liquid concentration. Zhan et al.[20] simulated grain morpholo
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