Some aspects of solidification: solute transport in the generation of microstructure

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Much of this applicant's research career has been concerned with the science and practice of solidification i.e. how to help the user to make better castings. The metal used for cast products is usually an alloy consisting of one element in abundance (the solvent) and smaller percentages of a number of other elements (solutes). When the liquid metal begins to solidify, the solutes tend to become localised in small regions of the casting and help to produce the 'microstructure' of the cast metal, important in determining the as-cast properties. Empirical knowledge is no longer sufficient to meet the current demand for a higher quality in surface finish and/or stronger products and so this has resulted in the casting process being 'numerically modeled', i.e. casting engineers develop a detailed understanding of the casting process itself and how small changes in (say) the temperature of the liquid metal when poured into the mold will affect the final microstructure and hence the final properties of the cast material. The development of a custom-built model is usually an imperative component of the design and operation of the larger scale industrial casting process if it is to be economically competitive with others. However, any computer model will only be as good as the accuracy of the physical and chemical data used by the modelers. Since the metal to be cast contains solute and that solute moves about - 'diffuses' - during the freezing of the alloy, it is imperative that accurate diffusion rates for the principal solutes be available. Since much of the published data in this area is not particularly accurate, the major aim of this proposal is to seek a better understanding of how such diffusion rates change with temperature. With respect to the training of HQP, the project involves the development of computational skills and precision with physical measurements - both of great importance in the Canadian workplace.