期刊
JOURNAL OF NON-CRYSTALLINE SOLIDS
卷 355, 期 52-54, 页码 2616-2621出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jnoncrysol.2009.09.003
关键词
Amorphous metals; Metallic glasses; Alloys; Diffraction and scattering measurements; X-ray diffraction; Microscopy; Scanning electron microscopy; TEM/STEM; Thermal properties; Calorimetry; Enthalpy relaxation; Glass transition; X-rays; Diffraction
资金
- Deutsche Forschungsgemeinschaft (DFG) [Al-578-6]
Enthalpy relaxation experiments were conducted to study the kinetics of free volume in Zr45.0Cu39.3Al7.0Ag8.7 bulk metallic glasses (BMGs) during isothermal relaxation using differential scanning calorimetry (DSC) at the temperature within the range from 648 to 684 K. Stretched exponential relaxation functions and the Sestak-Berggren SB (m, n) model were employed to analyze the kinetics of free volume. It is found that the relaxation time decreases from 2643.5 to 242.8 s while the Kohlrausch exponents increase from 0.717 to 0.892 in the investigated temperature range. The activation energy fluctuates slightly in the course of the relaxation process and its mean value is determined to be 239.7 kJ/mol. By fitting the first derivative of the conversion degree as a function of annealing time using the Sestak-Berggren SB (m, n) model, it is found that the values of m at all annealing temperatures are very small and can be approximated as zero. The values of the pre-exponential factors Z and the kinetic parameter n are found to be slightly varying with the annealing temperature, indicating the complexity of the kinetics of the isothermal relaxation. Finally, an approximate rate equation describing the kinetics of free volume during isothermal relaxation is proposed. (C) 2009 Elsevier B.V. All rights reserved.
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