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建立了二元系凝固过程通道偏析形成的数学模型,给出了描述焓与温度及固相分数耦合关系的表达式.在实验验证的基础上,对亚共晶与过共晶成分的NH4Cl-H2O侧向凝固通道偏析的形成位置与生长方向进行了数值模拟研究.模拟计算结果表明,偏析通道起源于糊状区,偏析通道中的富集溶质从糊状区流向液相区.为了维持偏析通道中的液体流动,枝晶间液体可通过糊状区从液相区得到补充.糊状区中富集溶质的流动方向取决于析出溶质的密度.NH4Cl-70%H2O侧向凝固时,析出的溶质密度较小,偏析通道倾斜向上生长,在糊状区上部形成A偏析.NH4Cl-90%H2O侧向凝固时,析出的溶质密度较大,在糊状区下部偏析通道倾斜向下生长.
The mathematical model for the formation of channel segregation in binary system was established and the expression describing the coupling between enthalpies and temperature and solid fraction was given.Based on the experimental verification, the relationship between hypoeutectic and hypereutectic composition of NH4Cl- H 2 O and H 2 O in the segregation channel.The results show that the segregation channel originates in the mushy zone and the enriched solute in the segregation channel flows from the mushy zone to the liquid zone.In order to maintain the segregation The liquid in the channel flows and the interdendritic liquid can be replenished from the liquid zone through the pasty zone.The flow direction of the enriched solute in the pasty zone depends on the density of the precipitated solute.NH4Cl-70% H2O precipitates laterally , The segregation channel grows obliquely upward, forming A segregation in the upper part of the mushy zone.During the lateral solidification of NH4Cl-90% H2O, the solute density is larger, and the segregation channel in the lower part of the mushy zone grows obliquely downward.