【作者】 孙强；

【导师】 张玉妥；

【作者基本信息】 沈阳理工大学 ， 材料加工工程， 2009， 硕士

【摘要】 凝固过程微观组织的模拟经历了由确定性方法、概率方法和相场方法的模拟;其中相场法是最新的方法,它可以模拟枝晶生长的过程。相场法是一种用于描述在非平衡状态中复杂相界面演变行为的强有力的工具。它不需要跟踪复杂液/固界面,就可实现模拟金属凝固过程中枝晶生长的复杂形貌。本文采用相场法,对Al-2-mole-%-Si合金凝固过程的多个枝晶生长和单个枝晶的定向生长进行了模拟,研究了相场模型参数对枝晶形貌的影响,主要内容如下:1.模拟了Al-2-mole-%-Si合金凝固过程多个枝晶生长过程,获得了具有多次分枝的枝晶形貌。不同取向的枝晶在熔液中自由生长,最终互相接触。再现了枝晶生长过程枝晶臂之间的竞争生长、枝晶之间的熟化和熔合现象。2.预测了Al-2-mole-%-Si合金凝固过程多个枝晶生长过程中溶质场分布。当枝晶尖端扩散场与相邻枝晶上生长出来的分枝的扩散场相遇时,枝晶停止生长。3.研究了相场模型中参数如:各向异性、过冷度、界面厚度和扰动对多个枝晶生长的影响。4.模拟了Al-2-mole-%-Si合金凝固过程单个枝晶的定向生长,不仅再现了凝固过程的枝晶生长,而且发现三次臂只在二次晶臂的一侧生长的这种特殊现象,这一模拟结果与Clicksman等人的实验吻合。更多还原

【Abstract】 The simulation of microstructure evolution during solidification has experienced deterministic method, stochastic method and phase field method. Phase field method is the newest method and it can simulate the growth of dendritic crystal. Phase field method is an effective tool to describe the complicate solid-liquid interface in non-equilibrium state. Without explicitly tracking the complex phase boundaries, it is expected to simulate the complex dendritic growth during the solidification processes.Taking Al-2-mole-%-Si alloy for example, this work aimed at simulating multiple grains growth and oriented growth during solidification by using phase-field method. The effect of model parameters on dendrite morphology was studied. The main contents are as follows:1. The dendritic growth of multiple grains of Al-2-mole-%-Si alloy during the solidification processes was simulated. Dendrite morphology of multiple branches was obtained. The arbitrarily oriented crystals grow freely in undercooled melt. Eventually, gains impinge against each other. The competitive growth of grains, ripen, coalescence and solute microsegregation in the dendritic growth are realized.2. The solute distribution of dendritic growth of multiple grains of Al-2-mole-%-Si alloy during the solidification processes was predicted. When the diffusion field of dendrite tip encounter diffusion field of dendritic branch growth from adjacent dendrite, the dendrites then stop growing.3. The influence of different anisotropy coefficients, disturbance intension, interface thickness and undercooling on dendrite morphology and distribution of solute for grains were studied.4. Oriented growth of single grain of Al-2-mole-%-Si alloy during the solidification processes was simulated. Not only the process of dendritic growth during solidification is reappearing, but also the asymmetry phenomenon is found in the secondary and tertiary arms. The side branching occurs only at one side of the arms, which are consistent to experiments made by Clicksman.更多还原