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arXiv 1707.08403cond-mat.mtrl-sci
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Al-Cu纳米结构硬化机理的原子学研究

Atomistic study of hardening mechanism in Al-Cu nanostructure

Satyajit Mojumder, Tawfiqur Rakib, Mohammad Motalab, Dibakar Datta

摘要:

纳米结构具有取代传统金属结构的巨大潜力,因为它们通过应变硬化显示出增强的机械性能。采用分子动力学模拟研究了晶粒尺寸对Al-Cu纳米结构强化机理的影响。采用嵌入原子法(EAM)势,对平均晶粒尺寸为4.57 ~ 7.26nm的Al-Cu(50- 54%Cu)纳米结构在50~ 500 K温度范围内进行了不同应变速率下的拉伸模拟。结果表明,纳米结构的破坏机制受温度、晶粒尺寸和应变率的影响。在300- 500 K的高温下,Al-Cu纳米结构的破坏强度随平均晶粒尺寸的减小而增大,并遵循Hall-Petch关系。当晶粒尺寸减小时,位错运动受到显著阻碍,这对纳米结构的硬化起着至关重要的作用。由于Al晶粒间的弱连接,其失效通常从晶粒处开始,并通过晶界滑动、扩散、位错成核和扩展等途径进行。我们还可视化了不同晶粒尺寸下的位错密度,以显示位错如何影响纳米尺度下的材料性能。这些结果将有助于进一步研究纳米结构的变形机制。

英文摘要:

Nanostructures have the immense potential to supplant the traditional metallic structure as they show enhanced mechanical properties through strain hardening. In this paper, the effect of grain size on the hardening mechanism of Al-Cu nanostructure is elucidated by molecular dynamics simulation. Al-Cu (50-54% Cu by weight) nanostructure having an average grain size of 4.57 to 7.26 nm are investigated for tensile simulation at different strain rate using embedded atom method (EAM) potential at a temperature of 50~500K. It is found that the failure mechanism of the nanostructure is governed by the temperature, grain size as well as strain rate effect. At the high temperature of 300-500K, the failure strength of Al-Cu nanostructure increases with the decrease of average grain size following Hall-Petch relation. Dislocation motions are hindered significantly when the grain size is decreased which play a vital role on the hardening of the nanostructure. The failure is always found to initiate at a particular Al grain due to its weak link and propagates through grain boundary (GB) sliding, diffusion, dislocation nucleation and propagation. We also visualize the dislocation density at different grain size to show how the dislocation affects the material properties at the nanoscale. These results will further aid investigation on the deformation mechanism of nanostructure.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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