Theory of rod eutectic growth under far-from-equilibrium conditions: Nanoscale spacing and transition to glass

Abstract The growth of eutectic under large undercooling conditions is important in obtaining nanoscale composite microstructures. Many glass-forming eutectic systems also exhibit a fine rod eutectic microstructure and often show a direct transition from eutectic to glass with increasing undercooling at the interface. A theoretical model of rod eutectic growth is developed in this paper, which quantitatively evaluates the system and growth parameters that will give rise to large undercooling at the interface. In addition to the diffusion and capillary undercooling, the model incorporates the effects of a sharp decrease in the diffusion coefficient that is exhibited by fragile glass-forming systems, the presence of highly nonlinear liquidus lines at large undercooling, and the effects of non-equilibrium at the interface. The results of the model are then discussed to obtain an insight into the system and growth parameters that are critical for obtaining a large undercooling at the eutectic interface, which is important in the design of nanoscale composite materials and in the selection of potential glass-forming systems.