在介观尺度上建立的材料微观组织演化模拟技术,对于揭示材料组织与性能之间的关系意义重大,如今已成为材料加工以及性能研究领域的热门方向.在金属材料经历铸造、增材制造和焊接等工艺过程时,对流会对枝晶、共晶等组织的转变过程产生直接影响.因此,在对凝固组织进行模拟时,考虑对流作用下的多相形核与生长情况至关重要.基于Phase Lab软件的凝固相场模拟功能进行拓展,构建了多序参量相场方程,并引入纳维-斯托克斯(Navier-Stokes,N-S)方程来描述流场的演化,同时将流场与相场控制方程耦合,进而实现了对对流作用下凝固组织演化过程的模拟功能.更进一步,借助随机形核理论对凝固过程中多相、多位点的自发形核过程进行描述,从而成功实现对复杂凝固过程的模拟.该模型已成功应用于合金在过冷条件下的均质形核,随后的核枝晶生长过程、两固相竞争协作生长所形成的片层状共晶组织,以及流动中固体相对运动等典型现象的模拟.
Simulation technologies for material microstructure evolution at the mesoscale are crucial for understanding the relationship between material microstructures and properties, and have become a prominent research direction in the fields of material processing and property studies. When metallic materials undergo processes such as casting, additive manufacturing, and welding, convection significantly influences the transformation of microstructures, such as dendrites and eutectics. Therefore, it is essential to consider multiphase nucleation and growth under convection in solidification microstructure simulations. This paper extends the solidification phase-field simulation capabilities of Phase Lab software by developing multi-parameter phase-field equations. The Navier-Stokes (N-S) equation is incorporated to describe the evolution of the flow field, and the governing equations for the flow and phase-field are coupled, enabling the simulation of solidification microstructure evolution under convection. Furthermore, by utilizing stochastic nucleation theory, the spontaneous multiphase, multi-site nucleation process during solidification is described, successfully simulating complex solidification processes. The model has been successfully applied to simulate typical phenomena, including homogeneous nucleation and dendritic growth of alloys under supercooling, the lamellar eutectic formation resulting from two-solid-phase competitive growth, and the movement of the solid phase in flow.
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