Crystallization kinetics of Cu55Hf45 glassy alloy

The crystallization kinetics of Cu55Hf45 glassy alloy were investigated under non-isothermal and isothermal conditions by differential scanning calorimetry. Under non-isothermal analysis the activation energies of glass transition and crystallization, at the onset and the peak crystallization temperatures were determined based on the Kissinger's method, the experimental values obtained were 700.8 ± 20.3 kJ/mol, 469.4 kJ ± 12.7/mol and 444.73 ± 14.2 kJ/mol, respectively. Under isothermal conditions, the crystallization kinetics was calculated by means of Johnson-Melh-Avrami equation and the activation energy was determined by using the Arrhenius equation. The average activation energy was 447.92 ± 16.1 kJ/mol and the average Avrami exponent value was n = 2.7, indicating that the crystallization mechanism implies a volume nucleation and two-dimensional growth. The local activation energy decreased as a function of the increment of crystallization volume, as when the crystallization progresses, the energy required for nucleation decreased and the value of activation energy drops.