In situ determination of γ′ phase volume fraction and of relations between lattice parameters and precipitate morphology in Ni-based single crystal superalloy

Diffraction profiles of single crystal Ni-based superalloy samples with different microstructures were measured in situ up to the complete solutionizing of the gamma' phase, using high resolution triple crystal diffractometer and high energy synchrotron radiation (150 keV, lambda = 0.08 Angstrom). A comparison between an undeformed sample and creep-deformed specimens with various resultant microstructures evidenced a relation between the lattice parameter distribution, the gamma' precipitate microstructure and the sign of the connectivity. It was shown that a deformation induces a change in the relative volume cell of gamma and gamma' phases. Moreover, the high resolution of the experimental set-up allows in many cases the gamma' phase volume fraction to be measured with a good accuracy. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.