Non-isothermal crystallization kinetics and fragility of (Cu _(46)Zr_(47)Al_7)_(97)Ti_3 bulk metallic glass investigated by differential scanning calorimetry

摘要

In this paper, bulk metallic glasses with the composition of (Cu _(46)Zr_(47)Al_7)_(97)Ti_3 were prepared by copper mold casting technique. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to investigate its structure and non-isothermal crystallization kinetics. DSC traces revealed that it undergoes two-stage crystallization. The activation energies corresponding to the characteristic temperatures have been calculated, and the results reveal that the as-cast alloys have a good thermal stability in thermodynamics. Based on Kissinger equation, the activation energies for glass transition, the first and second crystallization processes were obtained as 485 ± 16 kJ/mol, 331 ± 7 kJ/mol and 210 ± 3 kJ/mol, respectively, suggesting that the nucleation process is more difficult than the grain growth process. The fitting curves using Lasocka's empirical relation show that the influence of the heating rate for crystallization is larger than glass transition. Furthermore, the kinetic fragility for (Cu_(46)Zr_(47)Al_7) _(97)Ti_3 bulk metallic glasses is evaluated. Depending on the fragility index, (Cu_(46)Zr_(47)Al_7) _(97)Ti_3 bulk metallic glasses should be considered as "intermediate glasses".