Crystallization kinetics of the amorphous alloy Fe80B20 studied using a thermomagnetic balance

The kinetics of isothermal crystallization of the amorphous metal alloy Fe₈₀B₂₀ have been studied using a Perkin-Elmer thermomagnetic balance. Well-defined and reproducible incubation periods were observed on the degree of crystallization against time curves, in agreement with the theory of non-steady state nuclear ions in glasses. Values from 1.4 to 2.4 were obtained for the exponentn in the Johnson-Mehl-Kolmogorov-Avrami equation. The activation energy of viscous flow in the glass was found from the incubation period against temperature dependences at temperature near the crystallization point. The activation energy of crystallization was determined from the temperature dependence of the 50% crystallization times. Metallographic observations show unambiguously that two crystallization reactions proceed simultaneously: the growth of ready athermal centres located on the more slowly quenched surface of the amorphous metal ribbon along two directions, and growth in the bulk of the ribbon.