Molecular dynamics simulation of athermal heterogeneous nucleation of solidification
Molecular dynamics simulation of athermal heterogeneous nucleation of solidification
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DOI：
10.1016/j.commatsci.2019.03.061
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发表时间：
2019-06
影响因子：
3.3
通讯作者：
T. Fujinaga;Y. Shibuta
中科院分区：
文献类型：
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作者：
T. Fujinaga;Y. Shibuta
采用分子动力学模拟方法研究了过冷铝熔体中孕育晶粒细化剂的非热异质形核过程。立方相Ti颗粒的密堆积表面上出现一层薄的固体Al层，并生长为由面心立方（FCC）Al组成的球冠，而在其他表面上没有出现帽结构。有一个阈值过冷温度之间的停滞和自由生长的增长模式划分。由于临界过冷温度与有效粒子半径的倒数成正比，因此Ti粒子表面帽状形成被认为是非热异质形核。过冷熔融Al在平坦Ti表面上的固体生长的附加计算揭示了Ti表面上的初始固体形成是由吸附而不是经典的（即，热激活）异相成核。由于现有的自由生长理论模型中没有对非热异质成核过程进行原子级的描述，因此从原子级的角度研究非热异质成核的机理具有重要意义。
Athermal heterogeneous nucleation via grain refiners inoculated in undercooled Al melt is investigated by molecular dynamics (MD) simulations. A thin solid Al layer appears on close-packed surfaces of a cubic Ti particle and it grows to a spherical cap consisting of face-centered-cubic (FCC) Al, whereas no cap structure appears on the other surfaces. There is a threshold undercooling temperature dividing growth modes between stagnation and free growth. Since threshold undercooling temperature is proportional to the inverse of effective particle radius, cap formation at the surface of the Ti particle is regarded as athermal heterogeneous nucleation. Additional calculation of a solid growth of undercooled melt Al on the flat Ti surface reveals that initial solid formation on the Ti surface is caused by adsorption rather than classical (i.e., thermally–activated) heterogeneous nucleation. It is significant in this study to shed light on the mechanism of athermal heterogeneous nucleation from atomistic viewpoint since there is no atomistic description in an existing theoretical model of free growth.