Isochronal and isothermal crystallization kinetics of Zr–Al–Fe glassy alloys: Effect of high–Zr content

Abstract

The isochronal and isothermal crystallization behaviors of Zr70Al12.5Fe17.5 and Zr75Al7.5Fe17.5 glassy alloys were studied using differential scanning calorimeter (DSC). Under isochronal heating, the two amorphous alloys possessed different primary phases in the initial crystallization. The activation energies for the glass transition and crystallization of Zr75Al7.5Fe17.5 glassy alloy determined by the Kissinger, Ozawa and Augis–Bennett plots were larger than those of Zr70Al12.5Fe17.5 alloy. Isothermal kinetics of glassy alloys was modeled by the Johnson–Mehl–Avrami equation. For the Zr70Al12.5Fe17.5 glassy alloy, the Avrami exponents were mostly in the range from 2.48 to 2.68, which indicated a constant nucleation rate and a diffusion-controlled three-dimensional growth. The Zr75Al7.5Fe17.5 glassy alloy exhibited relatively larger Avrami exponents of between 2.72 and 3.07, implying a diffusion-controlled three-dimensional growth with increasing nucleation rate.