Crystallization kinetics of Zr60Al15Ni25 bulk glassy alloy

摘要

The crystallization kinetics of Zr60Al15Ni25 bulk glassy alloy under isochronal and isothermal conditions has been investigated by differential scanning calorimetry (DSC). The microstructure of as-cast Zr60Al15Ni25 bulk glassy alloy is observed by high-resolution electron microscopy (HREM). It is found that there exist nanocrystals with a size of about 7 nm in the glassy matrix, which are not observed in the XRD image. The results of Kissinger analysis show that the effective activation energies for glass transition (457 kJ/mol) and crystallization (345 kJ/mol) are high, indicating that it has large thermal stability against crystallization. The crystallization of Zr60Al15Ni25 bulk glassy alloy under isothermal annealing can be modeled by the Johnson-Mehl-Avami equation. The crystallization kinetics parameters show that the isothermal crystallization starts from the growth of the pre-existing nanocrystals and the crystallization process is diffusion-controlled. (C) 2004 Kluwer Academic Publishers.