Crystallization kinetics of Zr-24 at.% Fe amorphous alloy

Abstract

The process of crystallization in Zr-24at.%Fe amorphous alloy is of a polymorphic type in which the amorphous phase transforms without any change in composition to the Zr₃Fe crystalline phase. The kinetics of crystallization has been studied by differential scanning calorimetry. The activation energy of crystallization has been evaluated to be 270 kJ mol^-1 and 273 kJ mol^-1 by continuous heating and isothermal annealing experiments respectively. The Avrami exponent determined from isothermal annealing experiments has been found to be close to 3, a value which is consistent with the observed crystallization mode. The nucleation and growth kinetics of crystals in the amorphous matrix have been studied by quantitative transmission electron microscopy and the activation energies for the two processes have been independently determined. The observed nucleation and growth behaviours have been rationalized by considering the role of the quenched-in nuclei, the nucleation exponent, the growth exponent and the activation energies of nucleation and growth.