Crystallization of Bulk Zr 48 Nb 8 Cu 14 Ni 12 Be 18 Metallic Glass
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Crystallization of Bulk Zr48Nb8Cu14Ni12Be18 Metallic Glass Y.X. Zhuang, L. Gerward, J.Z. Jiang, J.S. Olsen,1 Y. Zhang,2 and W.H. Wang2 Department of Physics, Building 307, Technical University of Denmark, DK-2800 Lyngby, Denmark. 1 Niels Bohr Institute, Oersted Laboratory, DK-2100 Copenhagen, Denmark. 2 Institute of Physics, Chinese Academy of Sciences, Beijing, 100080, P.R. China. ABSTRACT The crystallization of bulk Zr48Nb8Cu14Ni12Be18 metallic glass has been investigated by differential scanning calorimetry (DSC) and X-ray powder diffraction. The activation energies of glass transition and crystallization for the glass obtained using Kissinger analysis from the shift of the peak temperature in the DSC curve are 470 and 235 kJ/mol, respectively. The effect of applied pressure on crystallization is studied by in situ high-pressure and high-temperature X-ray powder diffraction using synchrotron radiation. It is found that the crystallization temperature increases with pressure having a slope of 9.5 K/GPa in the range of 0-4.4 GPa.
INTRODUCTION The discovery of bulk metallic glasses with a wide supercooled liquid region and high thermal stability against crystallization offers a chance for investigating the glass transition, nucleation, and growth in the supercooled liquid region for a long scale time and exploring potential applications of metallic glasses [1,2]. Investigation of the crystallization process is of important for understanding the mechanisms of phase transformation far from equilibrium, for evaluating the glass forming ability of the melts and thermal stability of metallic glasses, and for producing controlled ultrarefine microstructures. This process is sensitive to the composition of materials and to external influence, e.g., applied pressure, annealing temperature, and heating rate. Schroers et al. [3] demonstrated that a heating rate of about 200 K/s prevents crystallization in bulk Zr41.2Ti13.8Cu12.5Ni10Be22.5 glass. In our previous works [4-7], we revealed that external pressure largely affects the crystallization temperature of bulk metallic glasses. The issue of the pressure effect on crystallization of metallic glasses is of interest from a fundamental viewpoint, and also with respect to the applicability of these materials by deformation in supercooled liquid region. In this work, the crystallization process of a Zr48Nb8Cu14Ni12Be18 bulk metallic glass with a supercooled liquid region [8] has been studied by differential scanning calorimeter (DSC) and X-ray powder diffraction (XRD). The activation energies of glass transition and crystallization for the glass are found to be 470 and 235 kJ/mol, respectively. The pressure effect on the crystallization process in the bulk glass was also investigated by in situ high-pressure and high-temperature X-ray powder diffraction using synchrotron radiation. It is found that the crystallization temperature increases with pressure having a slope of 9.5 K/GPa in the range of 04.4 GPa.
EXPERIMENTAL DETAILS
L5.2.1
The ingots, with composition Zr48Nb8Cu14
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