切向流动作用下的胞晶定向生长机理研究  

The mechanism of directional cellular growth with shear flow

作　　者：王建元[1] 翟薇[1] 金克新[1] 陈长乐[1] 

机构地区：[1]西北工业大学理学院,西安710072

出　　处：《物理学报》2011年第9期702-706,共5页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:50702046;61078057);西北工业大学基础研究基金(批准号NPU-FFR-JC200821;201048;2008KJ02031)资助的课题~~

摘　　要：实时观测了切向流动作用下SCN-0.2%Salol透明合金的定向胞晶生长过程,研究了切向流动作用对胞晶间距调整的作用机理.实验发现,切向流动使得胞晶阵列发生顺流偏转,并且稳态平均间距随流速的增高而减小.分析表明,这主要是由于流动作用导致胞端失稳波长减小而引起.施加切向流动使得胞晶间距的调整过程中的分裂机理多样化.顶端分裂由均匀分岔转变为多枝分岔和不对称分岔;同时,胞晶迎流侧容易产生分枝,且分枝生长方向在流动作用下转变为与胞晶主干方向相同.胞晶的淘汰机理由静态条件下的弱势生长胞晶被相邻两侧胞晶淘汰转变为切向流动作用下的上游生长占优势胞晶淘汰下游弱势胞晶.The directional cellular growth of SCN-0.2%Salol transparent alloy in the presence of shear flow at the liquid-solid interface is in-situ observed, and the cellular spacing adjusting mechanism is carefully investigated. It is found that the cellular array deflects forward the incoming flow direction, and the stable cellular spacing decreases with the increase of the flow rate. This is due mainly to the reducing destabilization wavelength caused by shear flow. Instead of the double symmetric splitting mode under static condition, the splitting mechanism of cellular growth exhibits multiplicity, which is characterized mainly by （i） multi-splitting and asymmetric splitting, and （ii） secondary branches appearing on the upstream side whose growth direction subsequently shifts to ward the direction paralleled to the trunk to form new cells. Meanwhile, the selected mechanism transits from the weak cells eliminated by the relatively strong ones on both sides during static solidification to the growth of weak cells on the downstream side suppressed by the stronger cells at the upstream side when shear flow is applied.

关 键 词：切向流动 定向胞晶生长 间距调整 

分 类 号：O781[理学—晶体学]