定向倾斜枝晶生长规律及竞争行为的相场法研究

采用多相场模型对定向凝固过程中倾斜枝晶生长进行了研究, 模拟了单一取向枝晶列的演化规律及不同取向枝晶列汇聚生长竞争淘汰行为. 结果表明, 枝晶尖端过冷度随倾斜角度的增大而增大, 即相同条件下倾斜枝晶尖端位置总是低于非倾斜枝晶; 汇聚生长时择优取向枝晶总是阻挡非择优取向枝晶, 但在抽拉速度较低时, 由于溶质扩散场的相互重叠, 晶界处择优取向枝晶的生长受到相邻非择优枝晶的影响而延缓, 这可能导致非择优取向枝晶淘汰择优取向枝晶.

Phase field modeling of the growth and competition behavior of tilted dendrites in directional solidification

The multi-phase field model is employed to simulate the growth of tilted dendrites during directional solidification. In this simulation, the evolution of a single oriented dendritic array and the overgrowth behavior between two converging grains with different orientations are studied. The simulated results show that the dendritic tip undercooling increases with the tilt angle, which means that the tip position of tilted dendrite is always lower than that of the non-tilted in the same condition. The favorably oriented grain always blocks the unfavorably oriented one in the case of converging growth. However, when the pulling velocity is low, the growth of the preferred crystalline orientation dendrites at the grain boundary is lagged by the immediate unfavorably ones because of the solutal interaction, which may result in the fact that the unfavorably oriented grain overgrows the favorably oriented one.