On the formation of Al3Ni2 intermetallic compound by aluminothermic reduction of nickel oxide

Simultaneous reduction of NiO and formation of Al3Ni2 intermetallic compound at 880, 940 and 1000 °C were investigated by means of the thermal reduction method. The optimal Ni contents for the starting samples were determined at different times and temperatures through the compositional analysis. The microstructure of the metallic quenched samples was observed by scanning electron microscope. Moreover, the X-ray diffraction analysis and energy disperse spectrometry were applied to characterize the formation of the phases. The results showed that the metallic samples consisted of Al3Ni2, Al3Ni and Al phases and that there was no trace of Ni, NiO and Al2O3. It was found that after 10 min at the applied temperatures, the reaction completed. For the longer time, the dispersed Al3Ni2 nuclei were grown and its continuous network formed. By increasing the temperature, the thickness of the Al3Ni precipitation around Al3Ni2 phase is enhanced in the samples with the same Ni content. A model was proposed for these reactions.