摘要
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 Zr41.2 Ti13.8 Cu12.5 Ni10 Be22.5(Vit.1)ribbons with a thickness of 40μm and 110μm and the strips with a thickness of 320μm and 490μm 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 320μm-thick strip is almost one magnitude lower than that of the single-roll produced 110μm-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.
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 Zr41.2 Ti13.8 Cu12.5 Ni10 Be22.5（Vit. 1） ribbons with a thickness of 40 μm and 110 μm and the strips with a thickness of 320 μm and 490 μm 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 μm-thick strip is almost one magnitude lower than that of the single-roll produced 110 μm-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.
基金
supported financially by the National Natural Science Foundation of China(Nos.51790484,51701213 and 51801174)
the National Key Research and Development Program of China(No.2018YFB0703402)
the Liaoning Revitalization Talents Program(Nos.XLYC1802078,XLYC1807062)
the China Postdoctoral Science Foundation(No.2018M633005)
the Dongguan Innovative Research Team Program(No.2014607134).
