Crystallization kinetics in Cu 46Zr 45Al 7Y 2 bulk metallic glass by differential scanning calorimetry (DSC)

Abstract

Crystallization transformation kinetics in isothermal and non-isothermal (continuous heating) modes were investigated in Cu 46Zr 45Al 7Y 2 bulk metallic glass by differential scanning calorimetry (DSC). In isochronal heating process, activation energy for crystallization at different crystallized volume fraction is analyzed by Kissinger method. Average value for crystallization in Cu 46Zr 45Al 7Y 2 bulk metallic glass is 361 kJ/mol in isochronal process. Isothermal transformation kinetics was described by the Johnson–Mehl–Avrami (JMA) model. Avrami exponent n ranges from 2.4 to 2.8. The average value, around 2.5, indicates that crystallization mechanism is mainly three-dimensional diffusion-controlled. Activation energy is 484 kJ/mol in isothermal transformation for Cu 46Zr 45Al 7Y 2 bulk metallic glass. These different results were discussed using kinetic models. In addition, average activation energy of Cu 46Zr 45Al 7Y 2 bulk metallic glass calculated using Arrhenius equation is larger than the value calculated by the Kissinger method in non-isothermal conditions. The reason lies in the nucleation determinant in the non-isothermal mode, since crystallization begins at low temperature. Moreover, both nucleation and growth are involved with the same significance during isothermal crystallization. Therefore, the energy barrier in isothermal annealing mode is higher than that of isochronal conditions.