Effect of annealing on the kinetics of glass transition and crystallization in Co–Fe–Ta–B amorphous alloy

The effects of pre-annealing near glass transition temperature on the kinetics of following glass transition and crystallization for Co43Fe20Ta5.5B31.5 amorphous alloy have been investigated by non-isothermal differential scanning calorimetry. It was found that pre-annealing diminished the kinetic effect of glass transition, whereas the kinetics effect of crystallization was not significantly affected by pre-annealing. The glass transition was delayed by pre-annealing, which is characterized by having higher glass transition temperature and activation energy of glass transition for annealed samples. The crystallization peak temperature corresponding to a selected heating rate was lower, but the activation energy of crystallization was higher for annealed samples than that for as-quenched samples. The contradiction between them was discussed in terms of the formation of clusters in the short-range order that had a similar structure of crystals precipitated from amorphous matrix and the small diffusivity in the annealed alloy. Based on Matusita's equation, it was found that the crystallization of as-quenched Co43Fe20Ta5.5B31.5 amorphous alloy was governed by diffusion-controlled two-dimensional growth of particles nucleated at constant rate.