强制对流作用下纯Ni枝晶生长的相场法研究(二)

Simulation of Dendritic Growth of Pure Ni Using Phase-field Model under Forced Flow Ⅱ

基于耦合流场的Wheeler模型,采用有限差分法对纯镍枝晶生长过程进行了模拟,研究了初始晶核半径对枝晶形貌及尖端生长行为的影响,分析了初始晶核半径大于尖端分裂临界晶核半径时的枝晶生长机理。结果表明,在流速为14.76 m/s的垂直强制对流作用下,初始晶核半径小于尖端分裂临界晶核半径时,不同初始晶核半径的枝晶臂尖端生长行为相似,且为抛物线形;初始晶核半径大于尖端分裂临界晶核半径时,晶核各优先生长方向上均形成两个突起,水平方向的两个突起合并粗化形成单一枝晶臂,逆流、顺流方向的两个突起平行生长形成尖端分叉的枝晶臂。

The phase field model based on Wheeler model coupled with the flow field was used to simulate dendrite growth of pure Ni by finite difference method. The effect of initial crystal radii on dendrite morphology and tip growth behavior of pure Ni was studied. Dendrite growth mechanism was analyzed when the initial crystal radii was larger than the critical initial crystal radii of tip branching-off. The result shows that, when the flow velocity is 14.76 m/s, dendrite arm tip growth behavior is similar and its shape is a parabola for various initial crystal radii that is less than the critical initial crystal radii of tip branching-off. Two protrusions are formed at the each priority growth direction of crystal and the two protrusions of horizontal direction merge coarsening to form a single dendrite, but the other two protrusions of longitudinal direction form dendrite whose tip is branching-off when the initial crystal radii is larger than the critical initial crystal radii of tip branching-off.