Fe-C合金枝晶生长过程的相场法模拟研究

发布时间：2018-04-20 11:12

本文选题：枝晶 + 相场模型　；参考：《中北大学》2017年硕士论文

【摘要】：枝晶作为金属晶体中的最基本结构,枝晶的生长过程对于金属铸件凝固组织的形成具有决定性作用。微观组织数值模拟作为一个新兴科学,由于其在金属枝晶生长及铸件成形过程模拟上拥有的独特优势而备受关注,它不仅能够有效地补充、完善金属凝固理论,而且能够指导实际生产从而降低工艺改进的成本。本文利用改进的相场模型对Fe-C合金进行了以下几个方面的研究。(1)利用改进的相场模型进行了枝晶生长过程的三维模拟。在相场理论的基础上,研究了相场模型参数(包括界面厚度、弛豫时间等)对于枝晶生长过程及最终形貌的影响,并确定合适的相场模型参数。(2)对等轴枝晶生长过程中枝晶尖端参数进行了分析,模拟结果与现有枝晶生长理论以及实验结果相一致。同时通过控制枝晶尖端过饱和度实现了成分过冷对枝晶尖端参数影响的定量化分析研究。(3)对等温凝固过程中等轴枝晶的生长过程进行三维模拟。利用耦合界面能各向异性的相场模型,研究了界面能各向异性对于枝晶生长过程的影响,并成功地模拟出Fe-C合金等轴晶生长过程中所存在的枝晶取向转变过程。(4)对定向凝固过程中枝晶的生长过程进行了分析,主要研究了推进速度、温度梯度对定向凝固过程的影响。通过调整定向凝固模拟过程中合金界面能各向异性系数实现对于不同含量的Fe-C合金定向凝固过程研究,成功模拟出定向凝固过程中所形成的的液相通道以及对应的溶质偏析现象,并系统的研究了定向凝固过程参数对于液相通道的形成以及整体枝晶形貌的影响。
[Abstract]:Dendrite is the most basic structure in metal crystals, and the growth process of dendrite plays a decisive role in the formation of solidification structure of metal castings. As a new science, numerical simulation of microstructure has attracted much attention because of its unique advantages in metal dendrite growth and simulation of casting forming process. It can not only effectively complement and perfect the theory of metal solidification. And can guide the actual production to reduce the cost of process improvement. In this paper, the improved phase field model is used to study the Fe-C alloy in the following aspects. 1) Three-dimensional simulation of dendritic growth process is carried out using the improved phase field model. Based on the phase field theory, the effects of phase field model parameters (including interface thickness, relaxation time, etc.) on the dendritic growth process and final morphology are studied. The parameters of dendritic tip in the process of iso-axial dendritic growth are analyzed. The simulation results are in agreement with the existing dendritic growth theory and experimental results. At the same time, by controlling the supersaturation of dendritic tip, the quantitative analysis of the effect of component undercooling on the dendritic tip parameters is carried out. The three-dimensional simulation of isometric dendritic growth during isothermal solidification is carried out. The effect of interfacial energy anisotropy on dendritic growth is studied by using the phase field model of coupling interface energy anisotropy. The dendritic orientation transformation process of Fe-C alloy during equiaxed crystal growth was successfully simulated. The dendritic growth process during directional solidification was analyzed. The effects of advancing speed and temperature gradient on the directional solidification process were studied. By adjusting the anisotropy coefficient of interface energy in the simulation of directional solidification, the directional solidification process of Fe-C alloy with different content is studied. The liquid channel formed during directional solidification and the corresponding solute segregation were successfully simulated, and the effects of directional solidification parameters on the formation of liquid channel and the morphology of dendrite were systematically studied.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG111.4

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