Nucleation and growth modes deduced from particle density distributions: Nanocrystallization of fcc Al in amorphous Al85Ni8Y5Co2

A general model to simulate the particle density distribution of a product phase upon phase transformation has been developed in a modular way. In particular, the influence of different nucleation and growth mechanisms known from solid-state phase transformations on the shape of the product phase particle density distribution has been investigated. The model has been fitted to experimental particle density distributions of nanoparticles of fcc Al developing in amorphous Al₈₅Ni₈Y₅Co₂ upon annealing for different times (1 minute to 2 hours) at various temperatures (473 to 508 K). Transient nucleation at a limited number of favored nucleation sites in combination with a two-stage growth mechanism (interface-controlled growth in the beginning and volume diffusion-controlled growth in the subsequent growth stage) very well describes the nanocrystallization process of amorphous Al₈₅Ni₈Y₅Co₂.