A study of two refractories as mould materials for investment casting TiAl based alloys

Interfacial reactions between Ti-46Al (at.%) casting and ceramic shell mould made of ZrO2 and Al2O3 were studied using a range of techniques. On the surface of the TiAl casting, a reaction layer as thick as 230 μm was found in the case of the zirconia mould, whereas there was no visible reaction layer for the alumina mould. Electron probe microanalysis indicated that elements of the two kinds of shell moulds diffused into the alloy melt during casting but to different extents. Metallographic analysis, microhardness measurements and composition analysis showed that alumina was stable and suitable for use as shell moulds when casting TiAl based alloys.