ω precipitation and its influence on the deformation mechanisms of a TNM Ti-Al alloy

Transmission electron microscopy is used to study the structure and morphology of nanoprecipitates of ω-type phase located in the β_o-phase of a TNM-TiAl alloy. Using conventional and high-resolution imaging techniques, it is demonstrated that this ω- 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 ω” phase.

Then, it is investigated how these nanoprecipitates affect the dislocation glide mechanism at room temperature in this β_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.