Liu Naijia, Sohn Sungwoo, Na Min Young, Park Gi Hoon, Raj Arindam, Liu Guannan, Kube Sebastian A, Yuan Fusen, Liu Yanhui, Chang Hye Jung, Schroers Jan
Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA.
Querrey Simpson Institute for Bioelectronics, Northwestern University, Evanston, IL, 60208, USA.
Nat Commun. 2023 Sep 26;14(1):5987. doi: 10.1038/s41467-023-41582-2.
The underlying atomistic mechanism of deformation is a central problem in mechanics and materials science. Whereas deformation of crystalline metals is fundamentally understood, the understanding of deformation of amorphous metals lacks behind, particularly identifying the involved temporal and spatial scales. Here, we reveal that at small scales the size-dependent deformation behavior of amorphous metals significantly deviates from homogeneous flow, exhibiting increasing deformation rate with reducing size and gradually shifted composition. This transition suggests the deformation mechanism changes from collective atomic transport by viscous flow to individual atomic transport through interface diffusion. The critical length scale of the transition is temperature dependent, exhibiting a maximum at the glass transition. While viscous flow does not discriminate among alloy constituents, diffusion does and the constituent element with higher diffusivity deforms faster. Our findings yield insights into nano-mechanics and glass physics and may suggest alternative processing methods to epitaxially grow metallic glasses.
变形的潜在原子机制是力学和材料科学中的一个核心问题。虽然晶体金属的变形已得到基本理解，但非晶态金属变形的理解仍较为滞后，尤其是对其中涉及的时间和空间尺度的确定。在此，我们揭示，在小尺度下，非晶态金属的尺寸依赖性变形行为显著偏离均匀流动，表现出尺寸减小变形速率增加以及成分逐渐偏移的现象。这种转变表明变形机制从粘性流动的集体原子传输转变为通过界面扩散的单个原子传输。转变的临界长度尺度取决于温度，在玻璃化转变时出现最大值。虽然粘性流动对合金成分没有区分，但扩散有区分，扩散率较高的组成元素变形更快。我们的发现为纳米力学和玻璃物理学提供了见解，并可能为外延生长金属玻璃提出替代加工方法。
