Analytical description of isothermal primary crystallization kinetics of glasses: Fe85B15 amorphous alloy

Kinetics of isothermal primary crystallization (formation of nanoscale crystals of α-Fe solid solution) of amorphous Fe85B15 melt-spun ribbons and structure of partially crystallized samples have been investigated by combination of the resistivity measurements and X-ray diffraction analysis. The simple analytical model describing kinetics of primary crystallization is developed. The model is based on the approximate solution of a steady state flux balance equation accounting soft impingement of the diffusion fields of growing crystals as well as on the Kolmogorov-Johnson-Mehl-Avrami formalism. It has been shown that the model allows to correctly describe the primary crystallization behavior, in part, the experimentally observed lowering of the Avrami exponent. By matching of the calculated kinetic curves with experimental ones with using a set of experimentally determined structural parameters the Arrhenius-type temperature dependence of the diffusion coefficient which governs the diffusion-limited growth of α-Fe crystals has been determined. A good agreement of such obtained values of diffusivity with the relevant experimental data implies the validity of the model for analysis of nanocrystallization kinetics in metallic glasses.