收稿日期: 2018-04-13
网络出版日期: 2018-12-21
基金资助
国家自然科学基金资助项目(51374141)
Induced solidification of liquid Al from molecular dynamics simulation
Received date: 2018-04-13
Online published: 2018-12-21
采用分子动力学(molecular dynamics,MD)方法模拟了嵌入不同半径(0.37~2.4nm)固态 Al 晶核的 Al 液诱导凝固过程. 结果表明,体系临界温度和嵌入晶核半径的倒数呈线性关系,符合吉布斯-汤姆森(Gibbs-Thomson, G-T)效应,得到的 G-T 系数 Γ 为 1.4*10-7 Km,体材料熔点 Tmbulk 为 (985.36±11.25) K.借助 Γ 计算出固液界面能为 (140.35±9.05)mJ/m2, 与通过毛细波动法获得的 149 mJ/m2 比较接近,再次证实了 Turnbull 的实验值(93 mJ/m2)$较低.外推得到诱导凝固失效半径为 0.91 nm,此时体系温度已达到临界温度极限值. 在该极限值下, 体系可以自发形核,孕育时间呈现随机性, 微观结构表现为不稳定的层错互相交织.在有效晶核尺寸范畴内, 孕育时间随嵌入晶核半径的增大而增加,长大速度却随半径的增大而降低, 微观结构是稳定的 lamellar 结构.
余熔刚, 赖琴梅, 汪昊, 吴永全 . Al 液诱导凝固过程的分子动力学模拟[J]. 上海大学学报(自然科学版), 2020 , 26(2) : 216 -226 . DOI: 10.12066/j.issn.1007-2861.2038
Molecular dynamics (MD) simulation was applied to analyze the solidification of liquid Al induced by embedded solid nanoparticles with radii ranging from 0.37 to 2.4 nm. It was found that the critical temperature was proportional to the inverse of the nucleus radius, i.e., Gibbs-Thomson (G-T) effect, through which the G-T coefficient Γ and the bulk melting temperature Tmbulk were obtained, 1.41.4*10-7 Km and (985.36±11.25) K, respectively. The solid-liquid interfacial energy which was estimated (140.35±9.05)mJ/m2 from Γ, was very close to the calculated 149 mJ/m2 by capillary fluctuation method. It proved again that Turnbull underestimated this quantity experimentally (93 mJ/m2). The critical failure radius was extrapolated to be 0.91 nm. Meanwhile, the corresponding system temperature had reached the lower limit for the critical temperature, under which the system could be spontaneously nucleated, and the incubation time was somewhat random. Besides, the microstructure was characterized by the metastable cross stacking faults. When the embedded nucleus could serve as the nucleation core, the incubation time increased with increasing embedded nucleus radius. However, the growth rate decreased separately with the increasing embedded nucleus radius. The microstructure adopted the relatively stable lamellar structure.
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