Real Time X-Ray Diffraction Study of the Formation by SHS of the Phases γ' and H in the Ternary System Al Ni Ti

Abstract
The formation of two compositions (A1_0.20Ni_0.75Ti_0.05 (γ') and A1_0.27Ni_0.50Ti_0.23(H)) in the ternary system Al Ni Ti by solid-state high temperature synthesis (SHS) was investigated. In addition Time-Resolved X-Ray Diffraction (TRXRD) studies were carried out using a synchrotron X-ray beam and a fast detection system to monitor the phase transformations. With a time resolution of 30 ms, it was possible to observe intermediate phases by scattering of the intense X-ray beam irradiating the sample surface during the passage of the combustion front. For the two reactions Ni(Al) was observed before the appearance of the final product. These experiments have been completed by Electron-Probe MicroAnalysis (EPMA) of sample in which the reaction had been stopped. They showed concentration gradients and transitory States. Moreover, we noted for the γ' formation a steady combustion propagation with a great speed while propagation of the combustion front for the H formation was pulsating. Associating these two techniques led to a better understanding of the different phenomena which exist during liquid-solid or solid-solid combustion reaction.