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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.
Based on the Eulerian-Eulerian method and the fluid volume technique, a three-dimensional multiphase hydrodynamic solidification model was established and coupled with the mass, momentum, solute and enthalpy conservation equations, the lateral solidification process of Fe-Pb alloy was numerically Simulation.Firstly, the influence of the distribution area quadratic gradient (SPb) and the concentration quadratic gradient (CPb) on the segregation mode is analyzed. The results show that the fluid phase transitions of liquid and gas phases make the segregation pattern appear as upper X-shaped lower V-shaped, X segregation by the vapor phase transformation driving force and multi-directional phase transition under the “scattering” formed; t> tc, with (SPb) and The angle of upper segregation angle and the angle of V segregation decrease and the yield of Pb increases, which is favorable for obtaining the solidified microstructure with stable dispersion.In addition, the formation mechanism of channel segregation under the interaction of liquid and gas is also studied, The results show that the channel segregation exists only in the region where the interaction between flow and phase changes (ul · cl and ug · cg) is negative. The flow perturbation in this region inhibits the local solidification of alloy and promotes the growth of segregation channel. The smaller the negative effect is, the more stable the segregation channel grows steadily If the results are consistent, the accuracy of the model is verified.