Crystallization kinetics of Zr-33 at % Ni amorphous alloy

Abstract

The amorphous to crystalline transition in Zr-33 at% Ni amorphous alloy has been found to occur by polymorphic crystallization. The product of the cyrstallization process has been identified as the equilibrium Zr₂Ni intermetallic phase. The kinetics of crystallization have been studied independently using differential scanning calorimetry (DSC) and transmission electron microscopy. The activation energy of crystallization has been evaluated by isothermal and continuous heating in DSC. The isothermal anneals have revealed that the crystallization follows the Johnson-Mehl-Avrami kinetics with an Avrami exponent close to 4. The microstructural changes accompanying crystallization have been studied for an interpretation of the Avrami exponent. The nucleation and growth rates of crystals have been estimated at different temperatures in order to determine the activation energies of the two processes. It has been found that nucleation is thermally activated and growth is interface controlled.