The geometry and microstructures of Al-Cu ribbons spun by planar flow casting have been investigated as functions of process parameters adapting various kinds of crucible materials and slot designs. The thickness ratio of the columnar layer to the entire thickness of the ribbon increased with increasing the wheel velocity and the superheat of molten metal before ejection. X-ray diffraction spectra indicated that there was an slight {200} preferred orientation on the wheel-side surface of the ribbon. A numerical model based on a two-dimensional cellular automaton technique coupled with the finite volume method was applied to predict solidification grain structure of the ribbon. The calculated grain structures were in good agreement with those obtained experimentally. Microstructural transition across the ribbon thickness has been investigated as a function of the solidification velocity based on microstructural observation of Al-4.3wt
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