Transmission electron microscopy is used to study the structure and morphology of nanoprecipitates of -type phase located in the o-phase of a TNM-TiAl alloy. Using conventional and high-resolution imaging techniques, it is demonstrated that this precipitation takes the form of needle-shaped nanoprecipitates that have characteristic dimensions of a few nanometers. Analyses of electronic diffraction patterns show that these precipitates are of a metastable " phase.

Then, it is investigated how these nanoprecipitates affect the dislocation glide mechanism at room temperature in this o-phase. For this purpose, quantitative measurements of densities of precipitates and of dislocation pinning points are developed. A comparison of these data indicates that only the largest precipitates serve as dislocations' pinning points.