Numerical modelling of tilt casting process for gamma-TiAl alloys

The tilt casting method is used to achieve tranquil filling of gamma-TiAl turbine blades up to 400 mm long. The reactive titanium alloy is induction melted in a cold crucible, and the crucible with the attached mould is then rotated through 180 degrees to transfer the metal into the mould. In the cold crucible, heat losses to the water cooled copper walls and base limit the superheat available, increasing the risk of premature freezing during mould filling. A compromise is required between fast and slow rotations to minimise the casting defects, such as misruns or gas entrainment. Simulations are presented using the authors' Computational Fluid Dynamics code with several novel developments in front tracking, heat transfer algorithms and turbulence model adaptation, which accounts for an advancing solid front. The computational results are validated against prototype castings produced at the University of Birmingham, and the model is then used to optimise the tilt casting process.