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采用落管方法实现了Ni 5 0 %Cu过冷熔体在微重力和无容器条件下的快速枝晶生长 .对微重力条件下的晶体形核和快速生长进行了研究 ,发现随着过冷度的增大 ,晶体生长形态由粗大枝晶向规划均匀的等轴晶转变 .实验中最大冷却速率达到 8× 10 3K s ,获得了 2 18K(0 14TL)的最大过冷度 .理论分析表明 ,过冷熔体中优先发生异质形核 ,形核率可达 10 1 2 m- 3s- 1 以上 ;Ni 5 0 %Cu过冷熔体中的枝晶生长随过冷度的增大发生由溶质扩散控制向热扩散控制的生长动力学机理转变 .在 6 8K过冷度条件下 ,生长界面前沿的偏析程序最大 .
The rapid dendritic growth of undercooled Ni 5 0% Cu under microgravity and vessel-free conditions was achieved by drop-pipe method.The crystal nucleation and rapid growth under microgravity conditions were studied and found that with the undercooling Degree of growth, the crystal growth morphology from the coarse dendrite to the planning of uniform equiaxed crystal transition in the experiment maximum cooling rate of 8 × 10 3K s, obtained 2 18K (0 14TL) of the maximum degree of undercooling. Theoretical analysis showed that , Heterogeneous nucleation is preferentially occurred in the undercooled melt, and the nucleation rate can reach over 10 1 2 m -3 s -1. The dendrite growth in the undercooled melt of Ni 5 0% Cu occurs with the increase of undercooling From the control of solute diffusion to the mechanism of thermal diffusion, the growth kinetics change.At the same time, under the condition of undercooling of 6 8 K, the segregation process of the front of growth interface is the largest.