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考虑了液态金属冷却定向凝固过程中动态对流边界,建立了高温合金铸件温度场数学模型,采用三维元胞自动机(cellular automaton,CA)方法和KGT生长模型,建立了镍基高温合金凝固过程晶粒形核及生长的数学模型.采用宏观模型与微观模型双向同步耦合,实现了温度场和晶粒组织的数值模拟.进行了浇注实验,用冷却曲线和晶粒形貌验证了数学模型的准确性.对液态金属冷却定向凝固规律的研究表明,抽拉速率不仅对糊状区形状有重要影响,而且对晶粒的平行度以及枝晶组织的细密性也有很大的影响.抽拉速率过小时,糊状区上凸,晶粒组织易发散;抽拉速率过大时,糊状区下凹,晶粒组织汇聚,同时造成枝晶组织的粗化;适当的抽拉速率下能获得平坦的糊状区,提高晶粒的平行度,细化枝晶组织.
Considering the dynamic convection boundary during directional solidification of liquid metal cooling, a mathematical model of temperature field of the high temperature alloy castings was established. The solidification process of Ni-based superalloy was established by using three-dimensional cellular automaton (CA) method and KGT growth model Grain nucleation and growth.Using the two-way simultaneous coupling of macroscopic model and microscopic model, the numerical simulation of temperature field and grain structure was realized.The pouring experiment was carried out, the mathematical model was verified by the cooling curve and grain morphology The research on the directional solidification of liquid metal cooling shows that the drawing rate not only has an important influence on the shape of the mushy zone but also greatly affects the parallelism of the grains and the densification of the dendritic structure. Hour, the mushy area is convex, the grain structure is easy to disperse; when the drawing rate is too high, the mushy area is concave and the grain structure is aggregated, and the dendritic structure is coarsened at the same time; Of the mushy zone, improve the parallelism of grains, refine the dendritic structure.