Grain-size dependence of the relationship between intergranular and intragranular deformation of nanocrystalline Al by molecular dynamics simulations
Grain-size dependence of the relationship between intergranular and intragranular deformation of nanocrystalline Al by molecular dynamics simulations
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DOI：
10.1103/physrevb.71.224110
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发表时间：
2005-06
影响因子：
3.7
通讯作者：
T. Shimokawa;A. Nakatani;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纳米晶铝的强度。纳米晶体模型组成的六方晶粒与晶粒尺寸$d$之间的5 nm和80 nm的变形通过施加张力。从晶粒尺寸硬化到晶粒尺寸软化的过渡可以在$d\ensuremath{\approx} 30\phantom {\rule{0.3em}{0 ex}}\mathrm{nm}$的区域观察到，这是强度的最佳晶粒尺寸。在晶粒尺寸硬化区，纳米晶模型主要通过晶内变形变形。因此，可以观察到位错的堆积。当晶粒尺寸变得小于30 nm时，其中晶界的厚度与晶粒尺寸相比不能被忽略，纳米晶体金属的主要变形机制是通过晶界滑动的晶间变形。此外，晶界滑动的几何失配容纳的晶粒旋转机制。此外，合作晶界滑动发生在5纳米模型。最佳晶粒尺寸由晶界过程抵抗晶间变形和晶界抵抗晶内变形之间的关系控制。因此，在观察到最佳晶粒尺寸的区域中，晶界的主要作用发生变化。
The strength of nanocrystalline aluminum has been studied using molecular dynamics simulation. Nanocrystalline models consisting of hexagonal grains with grain size $d$ between 5 nm and 80 nm are deformed by the application of tension. A transition from grain-size hardening to grain-size softening can be observed in the region where $d\ensuremath{\approx}30\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$, which is the optimum grain size for strength. In the grain-size hardening region, nanocrystalline models primarily deform by intragranular deformation. Consequently, a pile-up of dislocations can be observed. When the grain size becomes less than 30 nm, where the thickness of the grain boundaries cannot be neglected in comparison to the grain sizes, the dominant deformation mechanism of nanocrystalline metals is intergranular deformation by grain boundary sliding. Further, geometrical misfits by grain boundary sliding are accommodated by the grain rotation mechanism. Moreover, cooperative grain boundary sliding occurs in the 5 nm model. The optimum grain size is controlled by the relationship between resistance to intergranular deformation by grain boundary processes and intragranular deformation resisted by the grain boundary. Therefore, the primary role of the grain boundary changes in the region where the optimum grain size is observed.