基于纳米晶热力学特性表征函数, 将纳米晶热力学性质对晶界迁移的影响引入Cellular Automaton算法, 对纳米晶粒长大行为进行了定量化和可视化的仿真研究. 模拟结果表明, 纳米晶粒长大的动力学与传统粗晶材料不同, 在恒温条件下, 纳米晶粒的长大指数n不是常数(传统粗晶材料的晶粒长大指数n=2为常数), 随纳米晶粒长大过程的进行, n值从1.70至6.59发生变化. 作为纳米晶粒长大的驱动力, 纳米晶界的过剩自由能与纳米晶粒尺寸的变化直接相关. 由于纳米晶材料强烈的小尺寸效应, 纳米晶组织的热力学性质较大地影响纳米晶界的结构和能量状态, 从而影响纳米晶粒长大的动力学特征.因此, 只有结合纳米晶热力学特性的仿真研究才能获得对纳米晶粒长大行为本质性的认识.
Materials modeling and simulation have been widely used in studies on microstructure evolutions of conventional polycrystalline materials, but very few reports for uses in nanocrystalline materials. Based on our previous analytical model that describes the thermodynamic functions of nanograin boundaries (X.Song, J.Zhang, L.Li, et al, Acta Mater. 2006, 54(20), 5541-5550), the thermodynamic features of nanograin boundaries were introduced into the Cellular Automaton algorithm. With the hybrid model, the quantitative and visual simulations of nanograin growth have been carried out in this article. The simulation results show that the nanograin growth kinetics is different from the normal grain growth behavior in conventional polycrystalline materials. The nanograin growth exponent, n, is not a constant as in the polycrystalline metals which equals 2, but changes with the growing process, which has a range of 1.706.59. The excess free energy of the nanograin boundaries is the driving force for nanograin growth, which is closely related with the grain size. The simulation studies prove that the thermodynamic features of nanograin boundaries strongly affect the energy state of the nanocrystalline materials hence the nanograin growth kinetics, as a result of the nanoscale effect. It is considered by the authors that the simulations of nanograin growth should take into account the thermodynamic features of nanocrystalline materials.
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| [1] | |
| [2] | |
| [3] | |
| [4] | |
| [5] | |
| [6] | |
| [7] | |
| [8] |
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