Kinetics and mechanisms of two-stage crystallization of Fe₈₅B₁₅ amorphous alloy

The two-stage crystallization behavior has been experimentally identified in Fe₈₅B₁₅ metallic glass at isothermal and non-isothermal conditions involved appearance of primary α-Fe-based nanoscale particles in the first stage and polymorphic formation of Fe₃B crystals in the second step. An analytical model for description of two simultaneous processes in the Kolmogorov-Johnson-Mehl-Avrami formalism frameworks has been developed both for isothermal and constant rate heating conditions. The model is based on additivity of the extended volumes and on the assumption that growth of α-Fe nanoscale crystals is retarded due to diffusion field impingement. The calculated two-stage crystallization kinetic curves agree with those experimentally measured and the deduced values of free parameters are in reasonable accordance with the available ones.