Crystallization behavior of the Zr₆₁Al_7.5Cu _17.5Ni₁₀Si₄ amorphous alloy

The ribbons of amorphous Zr₆₁Al_7.5Cu _17.5Ni₁₀Si₄ alloy were studied by means of differential scanning calorimetry (DSC), X-ray diffractometry (XRD), high-temperature optical microscope and transmission electron microscopy (TEM). The activation energy for such the crystallization of the amorphous phase was about 360 and 370 kJ mole^-1 calculated by Kissinger and Avrami plots, respectively. Kinetics for the crystallization was analyzed by means of Johnson-Mehl-Avrami equation and discussed regarding to the value of Avrami exponent. The average value of the Avrami exponent n was measured about 2.43 at the range from 698 to 713 K. In addition, the cube of crystal size as a function of isothermally annealing time presents a linear relationship for the Zr₆₁Al_7.5Cu_17.5Ni₁₀Si₄ alloy. When the Zr₆₁Al_7.5Cu_17.5Ni ₁₀Si₄ alloy was isothermally annealed at 698 K, a Zr ₂Cu crystal with an average size of 105 nm was first observed at the early stage (30% crystallization) of crystallization. In addition, both nano-crystals of ordered fee ZrCu (∼100 nm) and ordered fcc Zr ₃Al (∼30 nm) were observed to precipitate from the amorphous matrix upon the middle stage (50% crystallization) of crystallization.