In Situ High-Energy X-ray Diffraction during Hot-Forming of a Multiphase TiAl Alloy

• Main Authors: Andreas Stark, Marcus Rackel, Aristide Tchouaha Tankoua, Michael Oehring, Norbert Schell, Lars Lottermoser, Andreas Schreyer, Florian Pyczak
• Format: Article
• Language: English
• Published: MDPI AG 2015-11-01
• Series: Metals
• Subjects: crystallographic texture; X-ray diffraction; synchrotron radiation; intermetallic alloy; titanium aluminides based on γ-TiAl; hot-forming; thermo-mechanical processing; phase constitution
• Online Access: http://www.mdpi.com/2075-4701/5/4/2252

Intermetallic γ-TiAl based alloys exhibit excellent high-temperature strength combined with low density. This makes them ideal candidates for replacing the twice as dense Ni base super-alloys, currently used in the medium temperature range (~700 °C) of industrial and aviation gas turbines. An important step towards the serial production of TiAl parts is the development of suitable hot-forming processes. Thermo-mechanical treatments often result in mechanical anisotropy due to the formation of crystallographic textures. However, with conventional texture analysis techniques, their formation can only be studied after processing. In this study, in situ high-energy X-ray diffraction measurements with synchrotron radiation were performed during hot-forming. Thus, it was possible to record the evolution of the phase constitution as well as the formation of crystallographic texture of different phases directly during processing. Several process temperatures (1100 °C to 1300 °C) and deformation rates were investigated. Based on these experiments, a process window can be recommended which results in the formation of an optimal reduced texture.