IN-SITU DETERMINATION OF GAMMA' 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 wit h different microstructures were measured in situ up to the complete s olutionizing 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' preci pitate microstructure and the sign of the connectivity. It was shown t hat a deformation induces a change in the relative volume cell of gamm a and gamma' phases. Moreover, the high resolution of the experimental set-up allows in many cases the gamma' phase volume fraction to be me asured with a good accuracy. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.