Growth of precipitates and changes in their morphologies
To observe precipitates in multiphase alloys (e.g. superalloys) different probes can be used. Microscopy and scattering methods are complementary tools for such investigations. Especially in scattering techniques using neutrons, diffraction and small-angle scattering provide information (from bulk samples) on the structure, morphology, size distribution and volume fraction of any inhomogeneities, e.g. precipitates embedded in a matrix. As an example of the unique possibilities in neutron research in-situ measurements at high temperature (up to melting point of the superalloys) could be done taking advantage of the large dimensions of a neutron beam and the easy handling of sample environment.
Fig. 1 shows a typical image of a multiphase superalloy which contain nano-sized co-precipitates of γ’ + γ’’. Changes of precipitate morphology caused by exposure at different temperatures were studied and some results are shown in Fig. 2.
