Recent Progress in the Development of Intermetallic γ-TiAl Based Alloys Enabled by In Situ Synchrotron X-Ray Diffraction and Scattering

Intermetallic titanium aluminide alloys based on the ordered γ-TiAl phase are innovative materials for lightweight high-temperature applications. In addition to their low density of roughly 4 g/cm³, their high specific Young’s modulus and strength even at elevated temperatures, and their good oxidation and burn resistance, especially their excellent creep properties make these alloys a material of choice for challenging structural applications. Following intensive research and development activities, γ-TiAl based alloys have recently entered service in the automotive and aircraft engine industries, <i>e.g.</i> as low-pressure turbine blades in environment-friendly jet engines, as engine valves in sports and racing cars, or as turbocharger turbine wheels. In the course of the past decades, the development of these complex multi-phase alloys has benefited greatly from the application of (<i>in situ</i>) synchrotron X-ray techniques. Diffraction and scattering techniques, in particular, have offered access to the atomic structure of the material and provided insights into a variety of microstructural parameters. Advanced experimental setups, which are steadily refined, have even allowed the exploration of elaborate manufacturing processes and yielded insights that have so far been inaccessible by means of conventional methods. Here, a practical introduction and overview of recent progress in this field of research are provided. Current prospects at modern synchrotron radiation sources will be illustrated by means of selected recent case studies pertaining to different stages in the development of modern γ-TiAl based alloys (<i>i.e.</i>, fundamental research, manufacturing, and fine-tuning of properties for application). In this context, available setups for <i>in situ</i> high-energy X-ray diffraction and small-angle X-ray scattering experiments will be discussed in terms of their advantages as well as their limitations. This talk reaches out not only to the TiAl scientific community, though. By addressing the key question as to how to actually simulate real-life conditions such as applied loads and high temperatures in a laboratory environment, researchers with a general background in materials science may also find in it a collection of ideas that are indeed applicable to many different materials systems.