Thin films of the organic molecule perylene-3,4,9,10-tetracarboxylic-dianhydride ("PTCDA") on graphite(0001) have been investigated from the mono-to the multilayer regime with low energy electron diffraction (LEED), X-ray-diffraction in Bragg-Brentano geometry, and high resolution scanning tunneling microscopy (STM). These different methods proved epitaxial growth in a coincident superstructure and yielded congruent results concerning details of the crystallographic structure of the epilayer. In addition it was possible to resolve submolecular structures in high resolution STM images; a comparison of the 10 resolved maxima of the tunneling current with the molecular structure leads us to question the conventional model description of tunneling.

Intermetallic γ-TiAl based alloys (”γ-alloys”) have a great potential to become important materials for advanced applications in aerospace, automotive and related industries. Research and development on γ-alloys have progressed significantly within the last decade. This research has led to a better understanding of the fundamental correlations between alloy composition and microstructure, processing behaviour and mechanical properties. This paper describes the progress in sheet rolling of γ-TiAl based alloys on industrial scale. Employing an advanced hot-rolling process sheets with lengths >1000 mm have been rolled. Furthermore, first results of foil rolling are presented. The mechanical properties of γ-TiAl sheet material with regard to processing route, alloy composition and microstructure are summarized and discussed. Sheet forming by means of superplastic forming and conventional metal forming techniques has successfully been conducted. Different joining techniques have been studied for γ-alloys including solid-state diffusion bonding. The oxidation resistance of γ-alloys is higher than that of Ti-alloys, however, for long-term applications at temperatures >700°C the need for reliable oxidation protective coatings is anticipated. Recent results of cyclic oxidation tests on coated γ-TiAl sheet are presented. Finally, the results of a stability test conducted on a γ-TiAl panel at 750°C are summarized.

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