Background: The solidification of metals is usually initiated by heterogeneous nucleation, which, however, is less controllable due to the unexpected impurities. In this study, the nucleation behavior of micro- and nano-sized Bi droplets embedded in the Cu matrix, where well-identified catalyst interfaces were introduced, was studied.

Objective: This paper demonstrated the nucleation behavior of the nano-sized Bi droplets embedded in the Cu matrix to determine the nucleation sites and contact angle.

Methods: Cu-20Bi (wt. %) melt-spun ribbons consisting of numerous micro- and nano-sized Bi droplets embedded in the Cu matrix were prepared. Based on the structure characterization by transmission electron microscopy (TEM), the nucleation behavior of these embedded Bi droplets was demonstrated by nanocalorimetry.

Results: The orientation relationship between the nano-sized Bi droplets and the Cu matrix was determined. The undercooling of the nano-sized Bi droplets with the cooling rate was more stable than that of the micro-sized Bi droplets, and a nucleation contact angle of 72o was obtained.

Conclusion: The undercooling increases with the reduction of droplet size. The nucleation of the Bi droplets is significantly affected by their interfacial structure with the Cu matrix. Compared with hexagonal Zn, the Cu matrix with face-centered cubic structure has a less catalytic effect on the nucleation of Bi.

背景：金属的凝固通常是由异相形核引发的，但是由于意外的杂质，这种形核的控制性较差。在这项研究中，研究了嵌入基质中的微米级和纳米级Bi液滴的成核行为，其中引入了公认的催化剂界面。

目的：本文证明了嵌入在铜基体中的纳米级Bi液滴的成核行为，以确定其成核位置和接触角。

方法：制备了由许多嵌入在铜基体中的微米级和纳米级Bi液滴组成的Cu-20Bi（wt。％）熔纺带。基于透射电子显微镜（TEM）的结构表征，通过纳米量热法证明了这些嵌入的Bi液滴的成核行为。

结果：确定了纳米级Bi液滴与Cu基体之间的取向关系。纳米级Bi液滴的冷却速度比微米级Bi液滴的冷却更稳定，成核接触角为72°。

结论：过冷度随着液滴尺寸的减小而增加。Bi液滴与Cu基质的界面结构显着影响其成核作用。与六角形的Zn相比，具有面心立方结构的Cu基体对Bi的成核作用较小。