Step-controlled Brownian motion of nanosized liquid Pb inclusions in a solid Al matrix
Step-controlled Brownian motion of nanosized liquid Pb inclusions in a solid Al matrix
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固体铝基体中纳米级液态铅夹杂物的步进控制布朗运动
DOI：
10.1016/j.actamat.2017.09.040
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发表时间：
2017-12-01
期刊：
影响因子：
9.4
通讯作者：
Dahmen, U.
中科院分区：
文献类型：
--
作者：
Radetic, T.;Johnson, E.;Dahmen, U.
我们用原位透射电子显微镜直接观察了固体铝中单个纳米级液态铅包裹体的布朗运动。发现该过程强烈依赖于夹杂物的大小和界面能的各向异性。速率控制机制主要是平衡形面的步骤成核和Al沿液固界面的扩散。由于Al-Pb界面在T-r近似为820 K时经历了一个粗化转变，阶跃成核势垒随着温度的升高而减小，并在Tr时完全消失。通过明确地包括温度依赖，我们证明了阶跃能量对数据的阿伦尼乌斯图的贡献斜率大于温度T时的实际活化能，其系数为T-r/(T-r-T)。此外，我们还表明，界面输运的扩散屏障起着实质性的作用。我们的分析调和了从温度和尺寸依赖过程中获得的活化能之间的巨大差异，并解决了观察到的一些粒子以非平衡形状冻结而附近较小的粒子足够移动以进行快速布朗运动的明显悖论。(C) 2017材料学报Elsevier Ltd.出版。版权所有。
We have made direct observations of the Brownian motion of individual nanosized liquid lead inclusions in solid aluminum by in-situ transmission electron microscopy. The process was found to depend strongly on the size of the inclusion and the anisotropy of the interfacial energy. The rate controlling mechanism was the nucleation of steps on facets of the equilibrium shape and the diffusion of Al along the liquid-solid interface. Because the Al-Pb interface undergoes a roughening transition at T-r approximate to 820 K, the step nucleation barrier decreases with increasing temperature and vanishes completely at Tr. By including the temperature dependence explicitly, we demonstrate that the contribution of the step energy to an Arrhenius plot of the data has a slope greater than the actual activation energy at temperature T by a factor T-r/(T-r-T). In addition, we show that the diffusion barrier for interfacial transport makes a substantial contribution. Our analysis reconciles a large discrepancy between activation energies obtained from the temperature and size dependences of the process and solves the apparent paradox posed by the observation that some particles are frozen in non-equilibrium shapes while nearby smaller particles are sufficiently mobile to undergo rapid Brownian motion. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.