Nanophotonics and Optoelectronics Research Center, Qian Xuesen laboratory of Space Technology, China Academy of Space Technology, Beijing, 100094, China.
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
Sci Rep. 2017 Jan 30;7:41365. doi: 10.1038/srep41365.
Both strengthening and weakening trends with decreasing diameter have been observed for metallic glass nanowires, sometimes even in the samples with the same chemical composition. How to reconcile the results has reminded a puzzle. Since the detailed stress state and microstructure of metallic glass nanowires may differ from each other significantly depending on preparation, to discover the intrinsic size effect it is necessary to study metallic glass nanowires fabricated differently. Here we show the complex size effects from one such class of metallic glass nanowires prepared by casting using molecular dynamics simulations. As compared with the nanowires of the same composition prepared by other methods, the cast nanowires deform nearly homogeneously with much lower strength but better ductility; and also show strengthening in tension but weakening in compression with decreasing wire diameter. The subtle size dependence is shown to be related to the key factors including internal and surface stress state, atomic structure variation, and presence of various gradients. The complex interplay of these factors at decreasing size leads to the different deformation behaviors.
金属玻璃纳米线的直径减小，其强度和弱化趋势都有观察到，有时即使在化学成分相同的样品中也是如此。如何调和这些结果让人想起了一个难题。由于金属玻璃纳米线的详细应力状态和微观结构可能因制备方法的不同而有很大差异，因此要发现内在的尺寸效应，有必要研究不同制备方法的金属玻璃纳米线。在这里，我们通过分子动力学模拟展示了一类使用铸造方法制备的金属玻璃纳米线的复杂尺寸效应。与通过其他方法制备的相同成分的纳米线相比，铸造纳米线具有较低的强度但更好的延展性，几乎均匀变形；并且还表现出随着直径减小，拉伸时增强而压缩时减弱的现象。这种微妙的尺寸依赖性与内部和表面应力状态、原子结构变化以及各种梯度的存在等关键因素有关。在尺寸减小的过程中，这些因素的复杂相互作用导致了不同的变形行为。
