L Granasy, T Pusztai, G -. Tegze, James A. Warren, Jack F. Douglas
Many structural materials (metal alloys, polymers, minerals, etc.) are formed by quenching liquids to form crystalline solids. This highly non-equilibrium process leads to an extraordinary variety of polycrystalline growth patterns that are broadly termed 'spherulites' because of their large-scale spherical shape. Despite the prevalence and practical importance of spherulite formation, only rather qualitative models of this phenomenon exist. The present work explores the growth and form of these structures, based on a coarse-grained field theory description. Our phase field simulations indicate that spherulitic growth is due to a randomisation of the local crystallographic orientation as new crystal grains nucleate at the growth front. We find that the diversity of spherulite patterns derives from the relative predominance of the influence of discrete local crystallographic symmetries versus the randomising effect of the secondary nucleation process. Faceted crystals and symmetric dendrites form when the first factor predominates, while the prevalence of the second factor ultimately leads to isotropic growth. We find that late-stage growth in the presence of a large driving force (super-cooling or supersaturation)approaches a universal spherulitic form with a radial needle-like fine structure, regardless of the early stage growth morphology.
Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)
, Pusztai, T.
, Tegze, G.
, Warren, J.
and Douglas, J.
On the Growth and Form of Spherulites, Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)
(Accessed March 4, 2024)