TiC–NiAl composites obtained by SHS: a time-resolved XRD study

Self-propagating high-temperature synthesis (SHS) has been performed in the quaternary Al–Ni–Ti–C system in order to obtain intermetallic–ceramic composites. These kind of reaction synthesis are very fast (linear velocity of the synthesis front is in the range 1–100 mm/s) and the productivity would be very high from the industrial point of view. Nevertheless, this characteristic is a negative point when synthesis mechanism and kinetics must be studied. There are only a few tools with enough time resolution in order to study these kinds of fast reactions. Synchrotron radiation (ESRF, Grenoble) has been employed to follow the reactions in situ on a time-scale of ∼100 ms. Powder diffraction patterns were recorded in this time-interval using a high-speed CCD camera coupled to an image intensifier X-ray sensitive detector with 1024×1024 pixels frames. As the reactions proceed patterns from the pre-heated, reaction front, post-heated and cooling zones of the reaction were sampled. The phases occurring during the reactions were identified and information of the reaction mechanism and the nucleation kinetics were obtained. SEM was used to characterize the final microstructure.