Effect of Vanadium on Grain Refinement of Aluminium
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Today, grain refinement of aluminium is effectively achieved by inoculation. The performance of the inoculants, as well as further growth restriction in the liquid metal, can be affected by alloy- elements and impurities. A trend towards increasing amounts of some specific impurities in the coke- anode bring forth increasing amount of these elements in the final metal. One such element is vanadium. The effect of limited amounts of vanadium on the grain refinement is in this thesis assessed. Both the impact on inoculation properties and continued growth restriction is investigated. Levels ranging from 0 to 500 parts- per- million (PPM) is evaluated in a commercial 6060- aluminium alloy and highly pure 5N (99.999 $\%$ Al)- alloy. Thermal analysis and optical microscopy are used to investigate the solidification and final microstructure. Edge- to Edge Mismatch (E2EM)- model, Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB) and Transmission Electron Microscopy (TEM) are applied to investigate the inoculants with respect to vanadium. Both theoretical and experimental evaluations indicate that vanadium has little or no effect on the grain refinement of aluminium at the investigated levels. Investigations of the inoculation particles also show that their composition and properties are unchanged. These results are consistent with the most recent literature.