Impact of short-range repulsive interactions between nuclei on the evolution of a phase transformation

The impact of short-range repulsive interactions between nuclei on the evol ution of a phase transformation is studied in order to describe quantitativ ely the kinetics of the transformation and to characterize systematically t he resulting microstructures. For these purposes both computer simulation a nd analytical methods are employed in order to investigate an idealized, tw o-dimensional model of nucleation and growth wherein nuclei contained in a background phase (e.g., liquid) interact via a "hard-core" repulsion, a pro totype for systems with a variety of possible interactions. Several quantit ies, including the dynamic area and perimeter fractions as well as the dist ribution of coalesced grain areas, are calculated. It is found, for example , that the temporal evolution of the system differs markedly from that in w hich the nuclei are spatially uncorrelated, particularly as the core diamet er becomes large relative to the characteristic internuclear separation for noninteracting nuclei, and an approximate, analytic description of this be havior is obtained. Finally, the morphologies of the grains constituting th e transformed microstructures are linked with the range of the internuclear interaction. (C) 2001 American Institute of Physics.