京都大学 / 新制・課程博士 / 博士(工学) / 甲第23502号 / 工博第4914号 / 新制||工||1768(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 平方 寛之, 教授 北條 正樹, 教授 嶋田 隆広, 教授 井上 康博 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

<p>Rapid solidification is a well established method to produce novel materials with improved mechanical or electrical properties. The sharp-interface kinetics of rapid solidification for a binary alloy is summarized. A Phase Field model mapping to this sharp interface model is summarized and solved by a new adaptive mesh refinement algorithm. Simulation results are consistent with experiments: The solidification velocity increases in power-law like fashion at low undercooling and approximately linearly at high undercooling; The solid/liquid interface undergoes a transition from four-fold dendritic to circular crystal structures; Solute trapping emerges and the solute partitioning approaches unity as the solidification velocity increases. Our Phase Field simulations are the first self -consistent predictions of velocity selection and morphological selection at both low and high undercoolings and also the first independent check of the solute trapping model in two dimensions.</p> / Thesis / Master of Applied Science (MASc)

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24890号 / 工博第5170号 / 新制||工||1987(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 嶋田 隆広, 教授 平方 寛之, 教授 井上 康博 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Dendritic solidification has been the subject of continuous research, also because of its high importance in metal production. The challenge of predicting macroscopic material properties due to complex solidification processes is complicated by the multiple physical scales and phenomena involved. Practical modeling approaches are still subject to significant limitations due to remaining gaps in the systematic understanding of dendritic microstructure formation. The present work investigates some of these problems at the microscopic level of interfacial morphology using phase-field simulations. The employed phase-field models are implemented within a finite-element framework, allowing efficient and scalable computations on high-performance computing facilities. Particular emphasis is placed on the evolution and interaction of dendrite sidebranches in the broader context of dendrite fragmentation, varying and dynamical solidification conditions.