Rejuvenated metallic glass strips produced via twin-roll casting

L Zhang and Y Wu and SD Feng and W Li and HW Zhang and HM Fu and H Li and ZW Zhu and HF Zhang, JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY, 38, 73-79 (2020).

DOI: 10.1016/j.jmst.2019.08.022

The energy state and atomic level structure of metallic glasses (MGs) are very sensitive to their cooling rates, and a lower cooling rate generally causes a lower energy and more relaxed state of MGs. In this work, the Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit. 1) ribbons with a thickness of 40 mu m and 110 mu m and the strips with a thickness of 320 mu m and 490 mu m were produced by single-roll melt spinning and twin-roll casting, respectively. The increase in thickness of either ribbons or strips results in a lower energy state with a smaller relaxation enthalpy, a lower content of free volume, and a higher hardness. Although the cooling rate of the twin-roll produced 320 mu m-thick strip is almost one magnitude lower than that of the single-roll produced 110 mu m-thick ribbon, the former, however, possesses a rejuvenated energy state as compared to the latter. Molecular dynamics simulations reveal that the squeezing force during twin-roll casting affects the evolution of connection types of clusters, and the 2-atom and 4-atom connections are prone to be retained, which results in a higher energy state of MGs. Such a rejuvenation process during twin-roll casting can overwhelm the relaxation process caused by the lower cooling rate. Therefore, twin- roll casting is not only a method being capable for producing strips with a large thickness, but also prone to obtain a high energy state of the MG strip. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

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