Gravity-driven Beryllium Transport in ZrTiCuNiBe Melt and its Influence on Glass Formation
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P. Liua) Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, People’s Republic of China
X.Y. Wang Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, People’s Republic of China; and Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China
Y.Z. Jia Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China; and School of Material Science and Technology, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
M.Z. Ma Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, People’s Republic of China
L.L. Sun Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China
W.K. Wang Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, People’s Republic of China; and Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China (Received 25 January 2005; accepted 2 March 2005)
Compositional and microstructural differences from bottom to top along a water-quenched Zr41Ti14Cu12.5Ni10Be22.5 alloy rod, 90 mm in length and 22 mm in diameter, were investigated experimentally by x-ray diffraction measurement, differential scanning calorimetry, and composition analysis. The results show that the upper part of the rod contains more beryllium atoms and is amorphous. The lower part with less beryllium atoms contains crystalline phases. The composition gradient is possibly due to the gravity-driven transport of Be-rich clusters and un-melted tiny solid pieces in the alloy melt.
I. INTRODUCTION
Atomic transport phenomena in the molten, supercooled, and glassy states of the multicomponent bulk metallic glass alloys have been widely investigated with quasielastic neutron scattering1,2 and radiotracer methods.3–8 Among these studies, diffusion behavior of beryllium, the smallest and possibly fastest diffusing component in ZrTiCuNiBe glass forming alloys, can be described by a modified Arrhenius expression5,7 by single atomic jumps in a slowly changing configuration of a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0306 2302
http://journals.cambridge.org
J. Mater. Res., Vol. 20, No. 9, Sep 2005 Downloaded: 09 Apr 2015
neighboring atoms6 in the supercooled liquid state. Transport of beryllium below the glass transition temperature (Tg) in the glassy state is mainly by a single atomic jump mechanism.6 However, beryllium transport behavior in ZrTiCuNiBe metallic melts above liquidus temperature and its influence on the glass formation have been ignored for a long time. The structures of metallic glasses are discussed in many literatures. The polycluster model,9 one of the most highly developed models describing the structure of the metallic glass, has usually been used to interpret the experimental data on the structure and properties of the
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