Small-angle neutron-scattering studies on oriented single-crystal superalloys

A single-crystal nickel-base superalloy SC16, recently developed for blade applications in land-based gas turbines, was investigated using the SANS instrument (V4) at the BERII reactor in HMI Berlin. The two-dimensional scattering patterns were measured as a function of the crystallographic orientation and analysed by comparing with iso-intensity profiles simulated on the base of a microstructural model of the SC16. Sizes, interparticle distances, volume fraction and morphology of precipitates were determined. Depending on the heat treatment conditions different scattering patterns were observed corresponding to different morphologies of γ′ precipitates. Additionally some samples showed streaks in the two-dimensional scattering patterns, indicating the presence of precipitates other than γ′. This was also confirmed by TEM, SEM and X-ray diffraction studies.