Nanocrystallization of Zr–Ti–Cu–Ni–Be bulk metallic glass

Abstract

The nanocrystallization kinetics of Zr 41.2Ti 13.8Cu 12.5Ni 10Be 22.5 (at.%) bulk metallic glass was investigated by differential scanning calorimetry (DSC) in the mode of continuous heating and isothermal annealing. In the case of continuous heating, three exothermic crystallization peaks can be observed, and the peak temperatures display a strong dependence on the heating rates, which can be fitted by a first order decay equation. The activation energies for crystallization are estimated to be E p1=166.83±8.85 kJ/mol, E p2=256.15±9.34 kJ/mol, E p3=174.36±12.56 kJ/mol, which correspond to peak temperatures of T p1, T p2, and T p3, respectively, indicating the formation of different crystallization phases at different stages. In the case of isothermal annealing, the crystallization products under isothermal annealing were observed and determined by transmission electron microscopy (TEM). The precipitation phases of the sample heated at higher temperatures were identified by X-ray diffraction (XRD), showing that the body-centered tetragonal (bct) Zr 2Cu and hexagonal ZrBe 2 are the primary phases, in spite of the presence of other phases. These results are consistent with the complexity of the DSC curves obtained during the continuous heating and isothermal annealing.