Journal
ACTA MATERIALIA
Volume 196, Issue -, Pages 88-100Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2020.06.008
Keywords
Metallic glass; Secondary relaxation; Synchrotron X-ray diffraction; Atomic cluster; Low-electron-density region
Funding
- National Science Foundation (NSF) of China [51671121, 51901122, 51871140]
- Research Grants Council (RGC) of the Hong Kong Government [CityU11200719, CityU11213118, CityU11209317]
- NSF of U.S. [DMR-1332208]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]
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Unusual secondary relaxations were revealed in metallic glasses (MGs) recently. In this paper, we explore the structural origins of secondary relaxations in La-based MGs alloyed with different species of elements. With the combination of synchrotron X-ray diffraction and ab initio molecular dynamics simulations, solute-atom-centered clusters with a string-like type of medium-range order are found in the MGs, the formation of which leaves dispersed low-electron-density regions. It is found the activation energy of fast secondary relaxation increases with the reduction of low-electron-density regions, while slow secondary relaxation relates to the distance of La in next nearest La-La atomic pairs and the size of the string-like solute-atom-centered clusters. The phenomena are interpreted within the framework of the generalized Maxell model and free volume model. Our results demonstrate fast secondary relaxation as the activation of a small concentration of liquid-like regions with extremely low viscosities preceding slow secondary relaxation, and provide evidence for the correlation of secondary relaxations with shortto medium-range electronic and atomic structure in MGs. (C) 2020 Published by Elsevier Ltd on behalf of Acta Materialia Inc.
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