高熵合金的特殊性質：簇-膠原子模型

海歸學者發起的公益學術平台

分享信息，整合資源

交流學術，偶爾風月

難熔性高熵合金具有高屈服強度和斷裂韌性，是結構應用的潛在候選材料。然而其力學性能的形成機制及其結構-主導力學性能的物理本質卻並不清楚。受金屬玻璃的啟發，來自中國西北工業大學的William Yi Wang帶領的研究團隊及其美國合作者，根據各原子尺寸與在周期表中位置，將一些原子劃歸聚合團簇，另一些原子劃歸粘合原子（起粘結團簇的作用）。採用分子動力學模擬方法構建了4種及以上元素組成的難熔高熵合金的不同原子排列方式。當合金從一種原子排列變為另一種原子排列時，伴隨著塑性變形中的化學鍵斷裂與形成，高熵合金和高熵金屬玻璃出現間歇性缺陷崩塌。他們發現高熵合金和高熵金屬玻璃的屈服強度由局部原子排列決定，是電子功函數的冪函數，並據此提出了價電子濃度分類原理（valence?electron-concentration-categorized principles），以及鋸齒行為的原子和電子相互作用基礎，為相關預測方法的開發和先進材料的快速設計奠定了基礎。npj Computational Materials3:23 (2017); doi:10.1038/s41524-017-0024-0; 標題與摘要如下，論文PDF文末點擊閱讀原文可以獲取。

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 (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.

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