The role of TCP structures in glass formation of Ni50Ag50 alloys

L Hu and Z Tian and YC Liang and TH Gao and Q Chen and Q Zheng and YX Luo and Q Xie, JOURNAL OF ALLOYS AND COMPOUNDS, 897, 162743 (2022).

DOI: 10.1016/j.jallcom.2021.162743

A molecular dynamics simulation of rapid cooling at a cooling rate of 10(11) K/s for Ni50Ag50 alloys was conducted. The rapid cooling process was analyzed by using the system energy, the pair distribution function, and the largest standard cluster analysis. It is found that with a crystallization-like energy curve the solidification of Ni50Ag50, alloy experiences a liquid-liquid and a liquid-solid transition (LLT and LST), finally result in an amorphous solid. In LLT stage the topologically close-packed (TCP) short-range order structures of both crystal (S666) and glass (S555) increase; whereas only glass medium-range order structures are formed. TCP-based long-range order (LRO) structures of glass do not increase until the beginning of the LST. Even in solid (T < T-g) the LRO parameter based on ICO structures fluctuates violently, while that based on TCP structures is quite stable. Therefore, TCP not only is the basic structural characteristics of disordered system but also reasonably represents the metastability of metallic glasses. These findings not only clarify the importance of LLT for the glass forming ability of alloys, but also fully demonstrate the effectiveness and necessity of TCP structures for describing the structure of amorphous systems. (C) 2021 Elsevier B.V. All rights reserved.

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