Fe-Pb合金凝固多相体系内偏析形成过程的三维数值模拟  

Three-dimensional modelling and numerical simulation on segregation during Fe-Pb alloy solidification in a multiphase system

作　　者：王哲[1] 王发展[1,2] 王欣[1] 何银花[1] 马姗[2] 吴振[2] 

机构地区：[1]西安建筑科技大学材料与矿资学院,西安710055 [2]西安建筑科技大学机电工程学院,西安710055

出　　处：《物理学报》2014年第7期240-254,共15页Acta Physica Sinica

基　　金：十二五期间国家科技支撑计划项目(批准号:2011BAE31B02)资助的课题~~

摘　　要：基于Eulerian-Eulerian方法和流体体积技术,建立了三维多相流体动力学凝固模型,并将其与质量、动量、溶质和热焓守恒方程相耦合,对Fe-Pb合金侧向凝固过程进行了数值模拟.首先,分析了分布面积二次梯度((SPb))和浓度二次梯度((CPb))对偏析模式的影响,结果表明:液、气两相的流动相变使偏析模式表现为上端X形下端V形,X偏析由气相相变驱动力和多取向相变作用下的"散射"形成;t>tc时,随(SPb)和(CPb)曲线降低,X偏析的下偏析角增大,上偏析角和V偏析角减小,Pb收得率增大,有利于获得含量稳定弥散的凝固组织.此外,还研究了液、气两相交互流动下通道偏析的形成机理,结果表明:通道偏析仅存在于流动-相变交互作用(ul·cl和ug·cg)为负值的区域,该区域的流动扰动抑制合金的局部凝固,促进偏析通道生长;流动-相变交互作用负值越小,偏析通道持续增长越稳定.模拟结果与实验结果相符合,验证了模型的准确性.The three-dimensional mathematical model for a three-phase flow during its horizontai solidification is studied using fluid dynamics method based on Eulerian-Eulerian and volume of fraction methods, in which the mass, momentum, species, and enthalpy conservation equations of the Fe-Pb alloy solidification process are solved simultaneously. Effects of Pb area quadratic gradient （△（△TSpb）） and Pb concentration quadratic gradient （△（△Cpb）） on the segregation formation are investigated. Results show that the segregation mode is manifested as X-segregates in the upper and V-segregates in the lower part during flow-solidification of liquid phase and gas phase. The X-segregates result from the phase transformation driving force of gas phase and ＂scattering＂ is due to the orientation of phase transition. When t 〉 tc the lower △（△Spb） and △（△TCpb） curves cause a larger yielding rate of Pb with a larger down angle of X-segregates and a smaller up angle of X-segregates and V-segregates. All these are favorable for the formation of a well-dispersed microstrueture. In addition, the gas-liquid two-phase flow interaction term has an effect on channel segregation, showing that channels occur only in the region where the flow-phase transition interaction term （ul· △7cl and ug· △cg） is negative. With a negative flow-phase transition interaction term the increase in flow velocity due to the flow perturbation and flow-phase transition interaction becomes more negative, thus the channel continues to grow and tends to be stable. Calculated results show good agreement with experimental data.

关 键 词：多相凝固 X形偏析形成 通道偏析 数值模拟 

分 类 号：TG111[金属学及工艺—物理冶金] O359[金属学及工艺—金属学]