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The global economic network, increasing mobility and wealth have a significant impact on energy consumption and environmental degradation, creating a serious social and political pressure on climate protection issues and a sustainable use of limited natural resources. In this context, a variety of programs are launched worldwide on a political and scientific / technical level to reduce aviation as well as automobile emissions. To meet these requirements, apart from new and improved design and lightweight construction concepts, high-temperature lightweight structural materials and their processing technologies play a key role. Due to their high specific (creep) strength and low density, intermetallic titanium aluminides have a particularly great potential, which is already being used industrially. While in the last decades, predominantly ingot metallurgical processes have been developed for the production of pre-material, which have subsequently been processed by casting and hot-working, the introduction of powder-based manufacturing technologies (e. g. additive manufacturing), with the availability of high-quality alloy powder, opens up new ways of material processing and component design. The basis of this work is the process-adapted 4th generation TNM-alloy, which was developed at the Chair of Physical Metallurgy and Metallic Materials. Due to its reactivity, manufacturing methods used are electron beam melting and laser powder-bed fusion as well as spark plasma sintering. Furthermore, high demands are placed on the production of the powder, in particular with regard to its purity. The chemical composition of the project alloy is designed and optimized so that it is “resistant” to the characteristics of the different manufacturing processes and their physical conditions. The starting powders and the manufactured specimens are subjected to a comprehensive characterization involving microstructural investigations on several length scales as well as the examination of the mechanical properties. Moreover, in order to further optimize the mechanical properties at elevated temperatures, it is an essential goal to develop suitable heat treatments. This work will show how conventional and high-resolution metallography can be used to combine innovative alloys with new processing technologies.

Intermetallic γ-TiAl based alloys are innovative lightweight structural high-temperature materials used in aerospace and automotive applications due to already established industrial-scale processing routes, like casting and hot-working, i.e., forging. A promising alternative method of production, regarding manufacturing of near net-shape components, goes over the powder metallurgy route, more precisely by densification of TiAl powder via spark plasma sintering. In this study, gas atomized powder from the 4th generation TNM alloy, Ti-43.5Al-4Nb-1Mo-0.1B (in at.%), was densified and the microstructure was investigated by means of electron microscopy and X-ray diffraction. The sintered microstructure exhibits lamellar α2-Ti3Al /γ-TiAl colonies surrounded by globular γ- and ordered βo-TiAl phase. The coarse lamellar spacing stems from the low cooling rate after densification at sintering temperature. Against this background, subsequent heat treatments were designed to decrease the lamellar widths by a factor of ten. Accompanying, tensile tests and creep experiments at different temperatures revealed that the modified almost fully lamellar microstructure is enhanced in strength and creep resistance, where a small volume fraction of globular γ-phase provides ductility at ambient temperatures.

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