2. Choice of shades

2.1 Limitations of the TiAl binary compound

A slight substoichiometry (52Ti-48 Al % at.) is favorable for obtaining a duplex or lamellar structure, guaranteeing improved ductility. Several factors are responsible for this beneficial effect: microstructural refinement, reduction in the covalent nature of atomic bonds, trapping of interstitial impurities by the α ₂ phase due to their high solubility in this phase, thus preventing these elements from segregating as oxides in the γ phase. Nevertheless, the binary compound Ti-48Al remains rather limited in hardening possibilities and its oxidation resistance can still be improved by the addition of additive elements. The extension of the application range to 850°C, or even 900°C with the addition...