Effect of overall composition on thermally induced solid-state transformations in thick EB PVD Al/Ni multilayers

Multilayered Ni/Al samples 20-70 μm thick of different average stoichiometries were prepared by electron-beam physical vapour deposition technique. The periodicity in the multilayers varied between 0.2 μm and 0.8 μm. The course of the solid-state transformations initiated by heating the samples at a constant rate has been studied. Intermetallic Al3Ni was found to be the first phase to form upon heating of all samples studied. Further reactions were dependent on the average composition of the sample so that Al-Ni compounds increasingly richer in Ni formed as the nickel content increased. In general, the phases Al3Ni, Al3Ni2, AlNi, and AlNi3 have been observed upon heating the samples to 600 °C. The phases were more likely to form in succession rather than to grow simultaneously.