Molecular Dynamics Study of Structure and Mechanical Properties of Grain Boundaries in Nanocrystalline Materials.
Molecular Dynamics Study of Structure and Mechanical Properties of Grain Boundaries in Nanocrystalline Materials.
复制标题
纳米晶材料晶界结构和力学性能的分子动力学研究。
DOI：
10.1299/kikaia.68.858
复制
发表时间：
2002
期刊：
影响因子：
--
通讯作者：
H. Kitagawa
中科院分区：
文献类型：
--
作者：
T. Shimokawa;A. Nakatani;H. Kitagawa
采用分子动力学模拟方法研究了铝纳米多晶（NPC）材料的晶界结构及其力学性能。采用嵌入原子方法（Mishin et al.1999）描述原子间相互作用。首先，双晶体模型进行了研究，以评估GB的能量，然后三种不同的NPC模型进行了检查，以调查晶粒尺寸的依赖性，并进行了计算拉伸试验的NPC模型。在双晶模拟中，将计算结果与有效介质理论、实验和从头算结果进行了比较，两者吻合较好。在NPC模型中，区分了位于GBs中的原子，并计算了GBs中原子的平均位能和平均比容。这些值与取向差角之间的关系表明，低角和高角晶界之间存在结构差异，边界约为20度。在模拟拉伸实验中，结果表明，GB滑移不仅与GB平面倾斜的Schmid因子有关，而且与GB特性有关，即在高能低密度的GB中观察到的滑移。在粗晶粒多晶体中，经常观察到不一定容易的小角度GB的迁移。结果表明，NPC材料的力学性能和变形机制与其微观GB特性密切相关，计算机模拟是评价GB特性和设计NPC材料不可缺少的工具。
Grain boundary (GB) structures of Al nanopolycrystalline (NPC) materials and their mechanical properties are studied by using molecular dynamics simulation. An embedded atom method (Mishin et al. 1999) is adopted to describe the interatomic interaction. First, bicrystal models are studied to evaluate the GB energies, then three different NPC models are examined to investigate the dependency of grain size, and a computational tensile test of a NPC model is carried out. In the bicrystal simulation, the result is compared with the effective medium theory, experiment and abinitio calculation and it corresponds well with them. Concerning NPC models, the atoms located in GBs are distinguished and the average site potential energy and the average specific volume over the atoms in GBs are calculated. The relation between these values and misorientation angles shows that there is a structural difference between low angle and high angle GBs and the border is about 20 degree. In the simulation of tensile test, the result shows the GB sliding is closely related to not only Schmid factor of inclination of GB plane but the GB character, i.e. it is observed at high-energy and low-density GB. Migrations of low angle GB that is not necessarily easy in coarse-grain polycrystals, are often observed. It is concluded that the mechanical properties and deformation mechanisms of NPC materials are closely related to the microscopic GB character and that the computer simulation play an important role as an indispensable tool to estimate GB character and to design the NPC materials.