Particularities of nucleation and growth of the B2-phase: Results of simulations for the Al50Ni50 alloy

We have studied mechanisms and kinetics of formation and growth of crystallization centers with the structure of B2-phase in the supercooled Al50Ni50 melts by means of molecular dynamics computer simulations. Visualization of the structure of supercooled melts is fulfilled and clusters with minimum potential energy are pictured separately. The dependence of critical sizes of nuclei on the supercooling is determined. Mechanism of nuclei formation is studied, and its particularities are discussed. We show that formation of critical nuclei occurs gradually by the way of improvement of structure in some areas of amorphous phase without their growth. Superstructure ordering in crystallization centers changes during their growth because of increasing of growth velocity at large supercoolings. Local displacements of the interface happen as a rule, when suitable changes of local structure in the amorphous phase near the interface boundary take place.