Entrained oxide films in TiAl castings

Tilt pouring of TiAl alloy from an induction skull melting (ISM) furnace into a ceramic shell mould has been carried out in this research. Microstructures and casting defects entrained by surface turbulence have been examined using scanning electron microscopy and EDX analysis. Oxide films were found draped over the dendrites of shrinkage porosity and the inner surface of bubbles in the experimental TiAl casting. The entrained oxide films act as heterogeneous nucleation sites, contributing to the formation of centre-line shrinkage porosity in the cast TiAl bars.