Effect of low level contamination on TiAl alloys studied by SIMS

Titanium aluminides are a valuable alternative to superalloys in applications where the ratio resistance/density is important. Since the ordinary production routes lead to high final costs, an alternative might be the use of traditional casting techniques by induction melting of the alloy in a ceramic crucible and pouring into ceramic moulds, made by the investment casting process. However, due to the high reactivity of Ti alloys, the use of traditional ceramic materials cannot be used, as they lead to oxide formation and oxygen pick up from both the crucible and the moulding materials. In this work, the effect of low level contamination was studied by SIMS. Special attention was given to the oxygen concentration for samples obtained with different mould materials. The comparison of SIMS in-depth profiles with hardness profiles, gives insight concerning the significance of the oxygen concentration in the properties of the alloy and regarding the choice of the most suitable materials for TiAl production. # 2004 Elsevier B.V. All rights reserved