Intermetallic Titanium Aluminides as Innovative High Temperature Lightweight Structural Materials – How Materialographic Methods Have Contributed to Their Development

Abstract

Abstract The present article is considered the continuation of the two review articles “Intermetallische γ-Titanaluminid-Basislegierungen aus metallographischer Sicht” (“Intermetallic γ titanium aluminide based alloys from a metallographic point of view”) by H. Clemens and F. Jeglitsch in Pract. Metallogr. 37 (2000) 194 – 217 and “Intermetallische γ-Titanaluminid-Basislegierungen aus metallographischer Sicht – eine Fortsetzung” (“Intermetallic γ titanium aluminide based alloy from a metallographic point of view – a continuation”) by H. Clemens and S. Mayer in Pract. Metallogr. 48 (2011) 64 – 100. With reference to a γ TiAl based alloy specifically developed for aircraft engines, the so-called TNM alloy, this third and concluding part describes how materialographic methods, in combination with a targeted use of complementary investigation methods, have contributed to their development, manufacture, and processing, and, eventually, to their industrial launch. In this context, the alloy development strategy is discussed and representative microstructures and nanostructures are shown and described after different processing and heat treatment processes. Selected case studies from materialographic examinations are presented and interpreted using, for each and every of these aspects, approaches from the fields of physical metallurgy und metal physics.