In this paper, the mechanical behavior of gradient nano-grained copper under uniaxial deformation was investigated using molecular dynamics simulations. The stress response was found to be different in the regions with different grain sizes, which was attributed to the different dislocation activities due to the dislocation-grain boundary synergies. The phenomenon of grain rotation was observed and a program was developed to accurately evaluate the grain rotation and explore its dependence on the grain size and the initial crystal orientation. It is found that all grains tend to rotate to the 30° orientation, consistent with the activation theory of the slip systems under the uniaxial deformation. The rotation magnitude is larger for larger grains, but the rotation rate is more diversely distributed for smaller grains, indicating more disturbance from grain boundary mechanisms such as the grain boundary sliding and the grain boundary diffusion for smaller grains. The effect of temperature on the grain rotation is also investigated, showing an increase of the dispersion of grain rotation distribution with the increase of temperature. This paper aims at providing insights into the synergistic deformation mechanisms from dislocations and grain boundaries accounting for the exceptional ductility of the gradient nano-grained metals.

中文翻译：

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基于分子动力学模拟的梯度纳米晶粒铜中形变引起的晶粒旋转

本文利用分子动力学模拟研究了梯度纳米晶粒铜在单轴变形下的力学行为。发现在不同晶粒尺寸区域的应力响应不同，这是由于位错-晶界协同作用导致位错活动不同所致。观察到晶粒旋转现象，并开发了一个程序来精确评估晶粒旋转并探索其对晶粒尺寸和初始晶体取向的依赖性。发现所有晶粒都倾向于旋转到30°取向，这与滑移系统在单轴变形下的激活理论一致。对于较大的谷物，旋转幅度较大，但是对于较小的谷物，旋转速率分布更多样化，表示来自晶界机制的更多干扰，例如较小晶粒的晶界滑动和晶界扩​​散。还研究了温度对晶粒旋转的影响，结果表明随着温度的升高，晶粒旋转分布的色散增加。本文旨在提供有关位错和晶界的协同变形机制的见解，从而说明了梯度纳米晶粒金属的出色延展性。