Al-Ni intermetallics obtained by SHS; A time-resolved X-ray diffraction study

Intermetallic compounds in the Al-Ni system were prepared by Self-propagating high-temperature synthesis (SHS). The front high speed in the range of 1-100 mm/s - typical of these processes made necessary the use a very intense synchrotron source (ESRF) coupled to a very fast acquisition system. Finely divided powders of Ni and Al were intimately mixed in a 1:1 mole ratio, and then compressed to form compact cylindrical of the right density to assure a steady combustion front. Diffraction patterns were acquired every 100 ms. As the reaction proceeded, patterns from the preheated, reaction front, post-heated and cooling zones were sampled. The crystal phases appearing were identified. Similarly, reaction mechanisms and nucleation kinetics were established. Also, high speed pyrometers were used to obtain combustion front temperature profiles and its propagation was video recorded. Finally, SEM images were taken to characterize the microstructure of end products.