Planar-flow spin casting: Momentum transport, vorticity transport, and texture formation

The planar-flow spin casting (PFSC) process is attractive to both industry and science. Industrial interest comes from novel microstructures and cost savings possible using PFSC. Scientifically, PFSC provides a test bed for studying phenomena such as the microstructure and contact lines where different materials and phases meet. These areas are not fully understood, and the interaction between industry and science is beneficial to both. A general understanding of how the ribbon thickness in PFSC depends on processing parameters exists. A broad goal of this work is to extend that understanding by considering ‘second-order’ effects on the process.; First the effect of viscosity is considered. A momentum transport model is developed using a boundary layer structure for the flow. The equations are averages across the narrow gap. Solidification changes the nature of one boundary layer from a classical Blasius layer to a suction-type layer. The analysis provides a prediction of the pressure field for comparison to experimental results. The model also includes vorticity in the bulk flow. A study of vorticity transport in boundary layers follows. Together these two models are establishing a base flow for PFSC. This base flow is necessary to further study issues in contacting and stability.; The importance of stability is seen in the quality of the as-cast ribbons. The ribbon exhibits various surface textures that are thickness variations occurring over small length scales. Textures are the result of flow or solidification instabilities. Two textures seen in experiments are presented. The textures are related to processing conditions to uncover possible sources. The results suggest areas to investigate and what additional data is needed.; Finally, the modeling is supported by experimental data. Important changes made to the existing apparatus are outlined. The impact of the improvements is demonstrated via experimental results. Besides better reproducibility, an emphasis is placed on simplification of the casting procedure. The final state of the caster is such that new researchers may begin to produce reliable data without difficulty.