Crystallization behavior of the Zr63Al7.5Cu17.5Ni10B2 amorphous alloy during isothermal annealing

The crystallization behavior of Zr63Al7.5Cu17.5Ni10B2 amorphous Alloy was studied by means of scanning differential calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM). A single stage transformation of the amorphous phase forming a Zr2Cu-type crystalline phase was observed. Kinetics for such single stage crystallization was analyzed by means of Johnson-Mehl-Avrami equation and discussed regarding to the value of Avrami exponent. In addition, the cube of crystal size presents a linear relationship with isothermal annealing time. This indicates that the crystallization process of Zr63Al7.5Cu17.5Ni10B2 amorphous alloy belongs to thermally activated process of Arrhenius type. From the HRTEM analysis, small amount of Zr2Cu-type crystals in the nano-scale dimension (10-20 nm) were observed to precipitate from the amorphous matrix upon the early stage of isothermal annealing the amorphous alloy at the temperature between the glass transition (Tg) and the onset crystallization temperature (Tx).