相场法模拟Ti-Al二元合金枝晶生长
发布时间：2018-12-06 20:36
【摘要】：Ti-Al基合金可在较高的温度下工作,且具有密度小、抗氧化、抗疲劳等性能。枝晶的形成对Ti-Al合金性能有很大影响,控制枝晶形貌对改善合金性能有着重要意义。枝晶凝固过程中受大量参数和复杂的边界条件影响,实际实验成本较高,使用计算机模拟可有效降低成本。本文首先对相场方法的发展及相关理论进行了论述。其次,以熵增加原理和热力学定律为基础,引入各项异性,构造了包括描述相场有序参数的方程,建立二元合金相场模型。再次,编写数值模拟程序,利用建立好的程序模型对Ti-Al二元合金的枝晶生长进行模拟。最后,研究了均匀温度场条件下各项异性系数、界面动力学系数以及界面能对枝晶的形貌和尖端生长速度的影响,初步研究了非均匀温度场条件下枝晶的生长情况。得到如下结论:1.各向异性强度对枝晶形成的影响主要体现在枝晶的形貌及生长速度上,在各向异性强度系数较小时枝晶不明显,当各向异性强度增大时枝晶也随之变成较为明显的树枝形态,并产生二次支臂,同时各向异性强度的增大还会加快枝晶的生长速度。2.界面能对枝晶形成的影响主要体现在枝晶的二次支臂上,当界面能较小时枝晶的形态无明显变化,随着界面能的增大,枝晶生长速度也加快,同时二次支臂的数量增多。3.各向异性强度系数对枝晶的影响同样体现在二次支臂上,界面动力学系数增大枝晶的生长速度也增大,随着运行时间的增大,枝晶受各项异性强度系数的影响也更为显著。4.非均匀温度场条件下,随着温度梯度的增大枝晶二次支臂的生长呈现明显趋势。
[Abstract]:Ti-Al-based alloy can work at high temperature and has low density, oxidation resistance, fatigue resistance and other properties. Dendrite formation has great influence on the properties of Ti-Al alloys, and controlling the dendrite morphology is of great significance to improve the properties of the alloys. The dendrite solidification process is affected by a large number of parameters and complex boundary conditions, and the actual experimental cost is high. Computer simulation can effectively reduce the cost. In this paper, the development of phase field method and related theories are discussed. Secondly, based on the principle of entropy increase and the law of thermodynamics, the equation including describing the ordered parameters of phase field is constructed, and the phase field model of binary alloy is established. Thirdly, a numerical simulation program is developed to simulate the dendritic growth of Ti-Al binary alloy. Finally, the effects of heterogeneity coefficient, interfacial kinetic coefficient and interfacial energy on the morphology and tip growth rate of dendrite under uniform temperature field were studied. The conclusions are as follows: 1. The effect of anisotropic strength on dendritic formation is mainly reflected in the morphology and growth rate of dendrite. When the anisotropic strength coefficient is small, the dendrite becomes a more obvious dendritic shape when the anisotropic strength increases. The secondary arm is produced, and the growth rate of dendrite is accelerated with the increase of anisotropic strength. The effect of interfacial energy on dendritic formation is mainly reflected on the secondary branch arm of dendrite. When the interfacial energy is small, the morphology of dendrite has no obvious change. With the increase of interfacial energy, the dendritic growth rate also accelerates, and the number of secondary branches increases. The effect of anisotropic strength coefficient on dendrite is also reflected on the secondary branch arm, and the growth rate of dendrite increases with the increase of interfacial kinetic coefficient. With the increase of running time, the dendrite is affected more obviously by the anisotropic strength coefficients. 4. Under the condition of inhomogeneous temperature field, the growth of secondary dendritic arms shows an obvious trend with the increase of temperature gradient.
【学位授予单位】：沈阳师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.23
本文编号：2366620
[Abstract]:Ti-Al-based alloy can work at high temperature and has low density, oxidation resistance, fatigue resistance and other properties. Dendrite formation has great influence on the properties of Ti-Al alloys, and controlling the dendrite morphology is of great significance to improve the properties of the alloys. The dendrite solidification process is affected by a large number of parameters and complex boundary conditions, and the actual experimental cost is high. Computer simulation can effectively reduce the cost. In this paper, the development of phase field method and related theories are discussed. Secondly, based on the principle of entropy increase and the law of thermodynamics, the equation including describing the ordered parameters of phase field is constructed, and the phase field model of binary alloy is established. Thirdly, a numerical simulation program is developed to simulate the dendritic growth of Ti-Al binary alloy. Finally, the effects of heterogeneity coefficient, interfacial kinetic coefficient and interfacial energy on the morphology and tip growth rate of dendrite under uniform temperature field were studied. The conclusions are as follows: 1. The effect of anisotropic strength on dendritic formation is mainly reflected in the morphology and growth rate of dendrite. When the anisotropic strength coefficient is small, the dendrite becomes a more obvious dendritic shape when the anisotropic strength increases. The secondary arm is produced, and the growth rate of dendrite is accelerated with the increase of anisotropic strength. The effect of interfacial energy on dendritic formation is mainly reflected on the secondary branch arm of dendrite. When the interfacial energy is small, the morphology of dendrite has no obvious change. With the increase of interfacial energy, the dendritic growth rate also accelerates, and the number of secondary branches increases. The effect of anisotropic strength coefficient on dendrite is also reflected on the secondary branch arm, and the growth rate of dendrite increases with the increase of interfacial kinetic coefficient. With the increase of running time, the dendrite is affected more obviously by the anisotropic strength coefficients. 4. Under the condition of inhomogeneous temperature field, the growth of secondary dendritic arms shows an obvious trend with the increase of temperature gradient.
【学位授予单位】：沈阳师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.23
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