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Atomic and electronic basis for the serrations of refractory high-entropy alloys(难熔性高熵合金锯齿形变形行为:原子和电子基础)
发布时间:2017-10-12

Atomic and electronic basis for the serrations of refractory high-entropy alloys(难熔性高熵合金锯齿形变形行为:原子和电子基础) 
William Yi Wang,Shun Li Shang,Yi Wang,Fengbo Han,Kristopher A. Darling,Yidong Wu,Xie Xie,Oleg N. Senkov,Jinshan Li,Xi Dong Hui,Karin A. Dahmen,Peter K. Liaw,Laszlo J. Kecskes&Zi-Kui Liu
npj Computational Materials 3, Article number: 23 (2017);
doi:10.1038/s41524-017-0024-0
Published online:29 June 2017
Abstract| Full Text | PDF OPEN

摘要:难熔性高熵合金具有引人注目的力学性能,即高屈服强度和断裂韧性,使其成为结构应用的潜在候选材料。从原子和电子相互作用层面上揭示高熵合金形成机制及其结构-主导的力学性能的物理本质至关重要,这种策略为进一步开发出预测方法、进而实现先进材料快速设计提供基础与保障。本研究报道了高熵合金和高熵金属玻璃[包括MoNbTaWMoNbVWMoTaVWHfNbTiZrVitreloy-1GG Zr41Ti14Cu12.5Ni10Be22.5]中的价电子浓度分类原理valenceelectron-concentration-categorized principles),观察了锯齿行为的原子和电子相互作用理论基础。我们发现高熵合金和高熵金属玻璃的屈服强度是由局部原子排列决定,电子功函数的幂函数定律。此外,键合电荷密度的相关性提供了对材料中松散键合位点性质的全新认识。强化学键团簇和弱化学键连接原子的同时出现暗示的高熵合金的锯齿形变形行为,进而揭示了缺陷运动的间歇性崩塌行为。  

Abstract:  Refractory high-entropy alloys present attractive mechanical properties, i.e., high yield strength and fracture toughness, making them potential candidates for structural applications. Understandings of atomic and electronic interactions are important to reveal the origins for the formation of high-entropy alloys and their structure−dominated mechanical properties, thus enabling the development of a predictive approach for rapidly designing advanced materials. Here, we report the atomic and electronic basis for the valence−electron-concentration-categorized principles and the observed serration behavior in high-entropy alloys and high-entropy metallic glass, including MoNbTaW, MoNbVW, MoTaVW, HfNbTiZr, and Vitreloy-1 MG (Zr41Ti14Cu12.5Ni10Be22.5). We find that the yield strengths of high-entropy alloys and high-entropy metallic glass are a power-law function of the electron-work function, which is dominated by local atomic arrangements. Further, a reliance on the bonding-charge density provides a groundbreaking insight into the nature of loosely bonded spots in materials. The presence of strongly bonded clusters and weakly bonded glue atoms imply a serrated deformation of high-entropy alloys, resulting in intermittent avalanches of defects movement.

Editorial Summary

High-entropy alloys: cluster-and-glue atoms behind exceptional properties(高熵合金:簇-胶原子模型揭示其优异性能) 

原子排列的“聚集-粘合模型”(cluster-and-glue model)解释了高熵合金的屈服强度和力学响应。受到金属玻璃的启发,来自中国西北工业大学的William Yi Wang带领的研究团队及其美国合作者,采用分子动力学模拟方法构建了由≥4元素组成的难熔高熵合金的不同原子排列方式。根据各原子尺寸与在周期表中位置,一些原子被划归聚合团簇,一些则被划 归为对团簇有粘结作用的原子。当合金从一个原子排列变化为另一个原子排列时,伴随着塑性变形中的化学键断裂与形成,高熵合金和高熵金属玻璃出现缺陷崩塌,从而解释了高熵合金的锯齿形力学响应。因此合金原子排列的理论将有助于预测高熵合金性质。 

A cluster-and-glue model of atomic arrangements explains the yield strength and mechanical response of high entropy alloys. Inspired by metallic glass, a team led by William Yi Wang at China’s Northwestern Polytechnical University and collaborators in the United States of America used molecular dynamics to build different atomic arrangements of refractory high entropy alloys consisting of four or more elements. Depending on atomic size and the periodic table group of each atom, some atoms organized into clusters while others glued the clusters together. Chemical bonds broke and formed with plastic deformation as the alloys went from one atomic arrangement to another via the glue atoms, causing defect avalanches explaining the serrated mechanical response of high entropy alloys.Taking into account atomic arrangement may thus help us predict the properties of high entropy alloys.

 
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