高熵合金的特殊性质：簇-胶原子模型

原创 2017-08-05 npj CM 知社学术圈

海归学者发起的公益学术平台

分享信息，整合资源

交流学术，偶尔风月

难熔性高熵合金具有高屈服强度和断裂韧性，是结构应用的潜在候选材料。然而其力学性能的形成机制及其结构-主导力学性能的物理本质却并不清楚。受金属玻璃的启发，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，根据各原子尺寸与在周期表中位置，将一些原子划归聚合团簇，另一些原子划归粘合原子（起粘结团簇的作用）。采用分子动力学模拟方法构建了4种及以上元素组成的难熔高熵合金的不同原子排列方式。当合金从一种原子排列变为另一种原子排列时，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间歇性缺陷崩塌。他们发现高熵合金和高熵金属玻璃的屈服强度由局部原子排列决定，是电子功函数的幂函数，并据此提出了价电子浓度分类原理（valence−electron-concentration-categorized principles），以及锯齿行为的原子和电子相互作用基础，为相关预测方法的开发和先进材料的快速设计奠定了基础。npj Computational Materials 3:23 (2017); doi:10.1038/s41524-017-0024-0; 标题与摘要如下，论文PDF文末点击阅读原文可以获取。

Atomic and electronic basis for the serrations of refractory high-entropy alloys

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

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 atomicand 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-1MG (Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5).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.