The directional solidification process is used to produce single crystal turbine blades for modern aero engines. The spacing of primary dendrites (PDAS) within the microstructure are an indication of the thermal gradient attained during solidification; process optimisation is being driven by the desire to refine the single crystal microstructure and maximise the thermal gradient which can reduce the propensity for defects, such as freckles, forming during solidification. Optimisation of the casting process also allows experimental materials to be investigated such as eutectic alloys, which require more stringent process conditions. A CFD-based method has been used in order to predict the thermal field within the ‘single shot’ Bridgman furnace and validated experimentally. The CFD model has been used to design an optimised heating element with the aim of increasing the thermal gradient achievable when casting single crystal alloys. Dendrite arm spacing has been measured from alloys cast using both heating element designs, with the concept experimental heating element showing a reduction in PDAS of up to 30% compared to the standard design for the same furnace conditions. The viability of casting eutectic alloys with such a furnace has also been assessed both experimentally and analytically using a CFD approach.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:600301 |
| Date | January 2014 |
| Creators | Dale, Steven |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.bham.ac.uk//id/eprint/4891/ |
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