Vogel, F.; Wanderka, N.; Balogh, Z.; Ibrahim, M.; Stender, P.; Schmitz, G.; Banhart, J.: Mapping the evolution of hierarchical microstructures in a Ni-base superalloy. Nature Communications 4 (2013), p. 2955/1-7

Phase separation of g0 precipitates determines the microstructure and mechanical properties of nickel-based superalloys. In the course of ageing, disordered g spheres form inside ordered (L12) g0 precipitates, undergo a morphological change to plates and finally split the g0 precipitates. The presence of g particles inside g0 affects coarsening kinetics and increases alloy hardness. Here we use atom probe tomography to visualize phase separation in a Ni86.1Al8.5Ti5.4 alloy in three dimensions and to quantify the composition of all the phases with near-atomic resolution. We find that g0 precipitates are supersaturated in nickel, thereby driving the formation of g particles and observe a compositional evolution of the g particles, which accompanies their morphological change. Our results suggest that by controlling nickel supersaturation we can tailor the phase separation and thereby the properties of nickel-based superalloys. DOI: 10.1038/ncomms3955 1