The present work investigates the dominant mechanisms in the plasticity of nano-sized fcc metallic samples. Molecular dynamics simulations of nanopillar compression show that plasticity always starts with the nucleation of dislocations at the free surface, and the crystal orientation affects the subsequent microstructural evolution. The Schmid factor of leading and trailing partials plays a decisive role in leading to the twinning, or slip deformation. A significant difference is observed in the strength of pillars of the same size with different orientations. The power-law equation exponent is completely dependent on the crystal orientations, and a weak or no size effect is observed in the compression of [100]- and [110]-oriented nanopillars. The observed orientation based behaviour decreases by confining the free surface.

中文翻译：

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晶体取向对纳米级 fcc 金属尺寸效应的影响

目前的工作研究了纳米尺寸 fcc 金属样品塑性的主要机制。纳米柱压缩的分子动力学模拟表明，塑性总是从自由表面位错的成核开始，晶体取向影响随后的微观结构演变。前部和后部分音的 Schmid 因子在导致孪生或滑动变形中起着决定性作用。在不同方向的相同尺寸的柱子上观察到显着差异。幂律方程指数完全取决于晶体取向，在[100]-和[110]-取向纳米柱的压缩中观察到微弱或没有尺寸效应。通过限制自由表面，观察到的基于方向的行为会减少。