The present paper summarizes our progress in establishing a novel production technology for -TiAl components to be used in advanced aircraft engines. In the beginning the main emphasis is put on the design of a -TiAl based alloy which exhibits excellent hot-workability. Then, the development of a “near conventional” hot-die forging route for this type of intermetallic material is described. Finally, the effect of two-step heat-treatments on the microstructure and the mechanical properties is discussed. Because of the small “deformation window” hot-working of -TiAl alloys is a complex and difficult task and, therefore, isothermal forming processes are favoured. In order to increase the deformation window a novel Nb and Mo containing -TiAl based alloy (TNMTM alloy) was developed, which solidifies via the β-phase and exhibits an adjustable β/B2-phase volume fraction. Due to high volume fractions of -phase at elevated temperatures the alloy can be hot-die forged under near conventional conditions, which means that conventional forging equipment with minor and inexpensive modifications can be used. Examples for the fabrication of -TiAl components employing a near conventional forging route are given. With subsequent heat-treatments balanced mechanical properties can be achieved. The results of tensile and creep tests conducted on forged and subsequently heat-treated TNMTM material are presented.

The C distribution within the -TiAl-phase of a Ti-45Al-5Nb-0.5C alloy with near- microstructure has been studied by atom probe tomography. In most areas the C atoms are homogenously distributed, and only a few C enriched features were detected which are presumably Cottrell atmospheres surrounding dislocation cores. The C concentration within the -phase was measured to be approximately 0.25 at.%, which is a factor of ten higher than the solubility limit reported for other TiAl alloys. The reason for this unusually high C solubility is explained by an existing model which relates the number of octahedral sites consisting of six Ti atoms to the solubility limit of interstitials. The large amount of C in solid-solution can explain the results of a recent study which showed that the C-containing alloy had an approximately 30% increase in yield strength when compared with a C-free sheet containing the same Ti, Al and Nb concentration.

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