Wang Zheng, Wang Wei-Hua
Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Natl Sci Rev. 2019 Mar;6(2):304-323. doi: 10.1093/nsr/nwy084. Epub 2018 Aug 24.
In a crystalline material, structural defects such as dislocations or twins are well defined and largely determine the mechanical and other properties of the material. For metallic glass (MG) with unique properties in the absence of a long-range lattice, intensive efforts have focused on the search for similar 'defects'. The primary objective has been the elucidation of the flow mechanism of MGs. However, their atomistic mechanism of mechanical deformation and atomic flow response to stress, temperature, and failure, have proven to be challenging. In this paper, we briefly review the state-of-the-art studies on the dynamic defects in metallic glasses from the perspective of flow units. The characteristics, activation and evolution processes of flow units as well as their correlation with mechanical properties, including plasticity, strength, fracture, and dynamic relaxation, are introduced. We show that flow units that are similar to structural defects such as dislocations are crucial in the optimization and design of metallic glassy materials via the thermal, mechanical and high-pressure tailoring of these units. In this report, the relevant issues and open questions with regard to the flow unit model are also introduced and discussed.
在晶体材料中，诸如位错或孪晶等结构缺陷是明确界定的，并且在很大程度上决定了材料的力学性能和其他性能。对于在没有长程晶格的情况下具有独特性能的金属玻璃（MG），大量研究致力于寻找类似的“缺陷”。主要目标是阐明金属玻璃的流动机制。然而，事实证明，它们的机械变形原子机制以及原子对应力、温度和失效的流动响应具有挑战性。在本文中，我们从流动单元的角度简要回顾了金属玻璃中动态缺陷的最新研究。介绍了流动单元的特征、激活和演化过程，以及它们与力学性能（包括塑性、强度、断裂和动态弛豫）的相关性。我们表明，类似于位错等结构缺陷的流动单元，对于通过对这些单元进行热、机械和高压剪裁来优化和设计金属玻璃材料至关重要。在本报告中，还介绍并讨论了与流动单元模型相关的问题和未解决的问题。
