定向凝固Ti-46at.%Al合金晶粒组织形成CAFE模拟  

Simulation of Grain Structure Formation of Ti-46at.%Al Alloy During Directional Solidification with CAFE Model

作　　者：刘东戎[1] 芦海洋 郭二军[1] 

机构地区：[1]哈尔滨理工大学材料科学与工程学院,黑龙江哈尔滨150080

出　　处：《哈尔滨理工大学学报》2017年第6期102-108,共7页Journal of Harbin University of Science and Technology

基　　金：哈尔滨市应用技术研究与开发青年后备人才项目(2014RFQXJ026);国家自然科学基金(51101045)

摘　　要：为了深入理解TiAl合金定向凝固过程中晶粒组织演化特点,采用CAFE模型(元胞自动机CA-有限元FE)模拟研究Ti-46at.%Al合金定向凝固过程中晶粒组织形成。借助文献中微重力定向凝固实验结果验证模型。考察了形核过冷度和自然对流强度对柱状晶向等轴晶转变(CET)、晶粒尺寸、晶粒延长因子以及偏析分布的影响。模拟结果表明:降低形核过冷度可以获得完全等轴晶组织。对于完全等轴晶组织,增大流动强度会加重铸件晶间偏析,而对凝固组织形貌以及晶粒尺寸、延长因子分布无影响。增加形核过冷度,发生CET。流动强度增加导致CET延迟,促进长形晶和等轴晶混合生长,增大晶粒尺寸和延长因子以及加重偏析。CAFE模型可以被用于预测TiAl合金晶粒组织形成以及分析控制机理。In order to deeply understand the mechanisms responsible for the grain structure evolution during directional solidification of Ti-46at.% alloy,characteristics of grain structure were simulated using CAFE model( Cellular Automaton-Finite Element). CAFE model was validated by comparisons with microgravity experiments from a reference. Influences of nucleation undercooling and natural convection intensity on columnar-to-equiaxed transition( CET),grain size,grain elongation and segregation were numerically investigated. Simulated results show that a fully equiaxed grain structure is obtained by lowering the nucleation undercooling. Increasing flow intensity aggravates intergranular segregation,but barely has effects on variations of grain structure morphology and distributions of grain size and elongation. With a high nucleation undercooling,CET occurs. By strengthening fluid flow,the occurrence of CET is retarded,a mixed structure of elongated and equiaxed grains is formed,both grain sizes and elongations are increased and segregation is enhanced. CAFE model can be used to predict grain structure evolution during solidification of Ti-46at.%Al and to analyze the controlling mechanisms.

关 键 词：Ti AL合金 CAFE模拟 晶粒组织 偏析 自然对流 

分 类 号：TG244[金属学及工艺—铸造]