基于微观形貌的逆偏析形成机理的数值模拟分析  

Numerical simulation study on the formation mechanism of reverse segregation based on microscopic morphology

作　　者：张宇[1] 朱宝丰 张士杰 张冰 张思雨 李日[1] ZHANG Yu;ZHU Baofeng;ZHANG Shijie;ZHANG Bing;ZHANG Siyu;LI Ri(School of Materials Science and Engineering,Hebei University of Technology,Tianjin 300401,China)

机构地区：[1]河北工业大学材料科学与工程学院,天津市300401

出　　处：《材料科学与工艺》2025年第1期31-40,共10页Materials Science and Technology

基　　金：国家自然科学基金资助项目(51975182)。

摘　　要：铸件中逆偏析的存在会显著降低铸件的力学性能和切削加工性能,因此研究逆偏析的形成机理具有重要意义。采用微观尺度的元胞自动机(CA)耦合格子玻尔兹曼方法(LBM)的模型,以Al-4.7wt.%Cu合金为例,分别模拟了计算域的全域柱状晶凝固、柱状晶向等轴晶转变(CET)的凝固和全域等轴晶凝固,并且分析了逆偏析的形成机理。研究发现,计算域边界较低的温度以及柱状晶发达的二次枝晶对含有溶质的熔体的分割阻碍是逆偏析形成的主要原因。计算域边界降温速度越快,逆偏析程度就越大;柱状晶对含有溶质的熔体的分割阻碍作用比中心等轴晶要大,凝固组织全部为柱状晶时,逆偏析最为严重,凝固组织同时含有柱状晶和等轴晶时,逆偏析次之,凝固组织全部为等轴晶时逆偏析最轻。计算域中心溶液受重力影响沿流场流向计算域底部的枝晶间隙,使计算域底部逆偏析程度大于其他部分。在铸锭凝固过程中可以考虑增加机械或者电磁搅拌、增大等轴晶区面积或者降低散热速率来降低逆偏析对铸锭的不利影响。The existence of inverse segregation in castings tends to significantly reduce the mechanical properties and machinability of castings and heightens the importance of investigating the formation mechanism of inverse segregation.A microscale cellular automata(CA)-coupled lattice Boltzmann method(LBM)model is established.The global columnar solidification,columnar to equiaxed transition(CET)solidification and global equiaxed solidification are simulated to analyze the formation mechanism of inverse segregation.The main reasons for the formation of inverse segregation are the lower temperature at the computational domain boundary and the separation of the solute-containing melt by secondary dendrites with the formed columnar crystals.A faster cooling rate at the computational domain boundary correlates to a greater degree of inversion.The inverse segregation of the computational domain with global columnar solidification is the most severe,followed with columnar to equiaxed transformation solidification,and the inverse segregation with global equiaxed solidification is the least severe.The reverse segregation at the bottom of the computational domain caused by gravity is greater than that of the rest.

关 键 词：逆偏析 元胞自动机 格子玻尔兹曼 微观形貌 数值模拟 AL-CU合金 

分 类 号：TG111.4[金属学及工艺—物理冶金]