【作者】 王帆；

【导师】 路阳；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2006， 硕士

【摘要】 随着航空业及汽车工业的发展,对铝合金铸件的需求量不断增大,同时对其致密性、微观组织和机械性能的要求也越来越高。用相场方法进行铝合金微观组织形成的模拟,对优化工艺参数、提高铸件质量,具有很重要的实际应用价值。本课题采用Al-2-mole-Cu合金为例去研究金属的凝固过程。 本文中,基于KKS模型,采用相场和溶质场两场耦合的方法对Al-2-mole-Cu合金凝固过程中枝晶生长进行了数值模拟。该模型从自由能入手,考虑了动力学各向异性和表面能各向异性的影响,为了模拟枝晶分枝的产生,在相场方程中加入了热扰动项。 本文采用Visual C++6.0实现程序的计算,为了提高计算效率和节省计算时间,应用直接差分去求解两场方程,实现宏、微观场之间的耦合,然后以.TXT方式输出计算结果,最后利用Tecplot9.0实现结果的可视化。 在模拟过程中,本文从单个晶粒的枝晶生长逐渐扩展到多晶粒相互影响下的枝晶生长,主要研究了各向异性系数、初始晶核浓度梯度与各向异性系数耦合、各向异性系数与过冷度耦合对单晶粒枝晶生长及溶质场分布的影响;溶质偏析对两晶粒枝晶生长与溶质分布的影响;过冷度对多晶粒枝晶生长与溶质分布的影响。模拟逼真的再现了二元合金枝晶的生长和择优等现象。最后,为了验证所建立的二维相场模型以及宏微观耦合方法,对Al-2-mole-Cu合金模拟结果与实验的金相照片进行对比发现,其预测枝晶形貌和实验结果吻合良好。更多还原

【Abstract】 With the development of aviation automotive industry, the production of aluminum alloy castings is increasing rapidly, and the quality of the castings including soundness, microstructure, and mechanical properties is more strict. Modeling of microstructure formation using phase-field model will help to evaluate and optimize the castings processing technology so as to improve their quality, we use Al-2-mole-Cu alloy as an example to study the solidfication because good properties of corrode -resistant and wearable.In this paper, the phase-field model basing on KKS model which coupled the concentration field is used to simulate microstructural dendrite growth of multiple grains for Al-2-mole-Cu alloy. The anisotropies of surface energy and kinetics are considered and the thermal noise is introduced into the energy conservation equation;In the process of simulation, the Visual C++ 6.0 was used to calculate the programme and the Tecplot 9.0 was used to achieve the vision of results.In order to save time of calculation and improve the efficiency, an interpolative method is used to achieve the coupling of the macro field and the micro field.In simulation, the growth of dendrites was expanded from single grain to multiple grains, we mainly studied the influence of different anisotropy coefficients、 the grads of solute for initial core coupling with anisotropy coefficients、 undercooling oupling with anisotropy coefficients on shapes of dendrites and distribution of solute for single grain;The influence of solute segregation on shapes of dendrites and distribution of solute for two grains and the influence of undercooling on shapes of dendrites and distribution of solute for multiple grains. The perferred growth and any other phenomenons of dendrite growth were reappeared in the simulation. At last, In order to verify the established 2-D model and macro coupled with micro method, the results of simulation are compared with the experimental optical microgaphs of Al-2-mole-Cu alloy, and the predicted dendrite shapes show good agreement with the experiments.更多还原