Driving forces for crystal nucleation in Fe–B liquid and amorphous alloys

The Fe–B system has been reassessed in order to model metastable and amorphous phases. An excess specific heat term has been added to describe Gibbs free energy of the liquid phase on undercooling and glass transition has been considered as a second-order transition. In addition, a recently proposed description of pure Fe lattice stabilities has been used for this optimisation. Stable and metastable phase diagrams have been calculated, as well as thermodynamic properties, which turn out in agreement with experimental data. Thermodynamic driving forces for crystal nucleation have also been evaluated for liquid and amorphous phases. According to experimental findings, it was found that the first nucleating phase is b.c.c. Fe for B-poor amorphous alloys. However, for B-rich compositions, a competition between Fe2B and Fe3B nucleation has been evidenced. A full explanation of the crystallisation process requires the evaluation of interfacial energies.