Dr. Christian Rockenhäuser Dr. Mario Metzger Philipp von Hartrott Prof. Birgit Skrotzki
This paper describes the degradation process of alloy 2618A due to coarsening of the S-phase. To quantitatively investigate the coarsening process dark-field transmission electron microscopy (DFTEM) was performed to investigate samples in different ageing states. The resulting particle size distributions allow a statistically relevant evaluation of the average particle radii. A fast increase of the average precipitate radii was found during the initial state of ageing for both the samples heat treated without external load and the crept samples. The authors suggest that the fast coarsening during the initial phase of ageing elapses fast due to the combined coarsening of the S-phase precipitates and the transformation of GPB zones into S-phase precipitates. After about 2500 h only S-phase precipitates remain and the coarsening process slows down.