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实时观察研究了切向流动作用下,丁二腈(SCN)-2%(质量分数)H2O合金熔体固液界面形貌随抽拉速度的变化规律.当抽拉速度较低时,切向流动作用能够提高平界面的稳定性.在中等抽拉速度区域内,液固界面形态并非稳态,而是随着抽拉速度的提高,分别经历了“平界面-胞状界面”和“胞状界面-枝晶界面”两种周期性振荡过程.分析表明,振荡生长模式的形成主要有以下两个原因:(ⅰ)流场对于界面的稳定作用与抽拉速度对界面的不稳定作用之间存在相互竞争,这是振荡界面产生的驱动力;(ⅱ)稳态溶质扩散场的建立需要一定的弛豫时间,这促使界面形态总是以平衡位置为中心振荡生长,而不能保持稳态生长.随着抽拉速度的提高,其对界面形貌的控制逐渐趋于主导地位,界面发展成为稳态的枝晶生长.
The effect of tangential flow on the morphologies of the solid-liquid interface of 2% (mass fraction) succinate (SCN) H2O melt with the drawing speed was investigated in real time. When the drawing speed is low, The fluid-liquid interface can improve the stability of the flat interface.In the area of medium drawing speed, the liquid-solid interface morphology is not steady state, but with the increase of drawing speed, the liquid-solid interface experiences “flat interface-cell interface” The results show that there are two main reasons for the formation of oscillation growth mode: (i) the instability of the interface between the flow field and the pulling speed (Ii) The establishment of a steady-state solute diffusion field requires a certain relaxation time, which encourages the interface morphology to always oscillate around the equilibrium position and can not be maintained Steady-state growth.With the increase of drawing speed, the control of the interface morphology gradually became dominant, and the interface developed into steady-state dendrite growth.