COMPOSITION-DEPENDENT STRUCTURAL AND MORPHOLOGICAL-CHANGES IN NICKEL-ALUMINUM FILMS PREPARED BY CO-EVAPORATION OF THE PURE METALS

The pure metals nickel and aluminium were evaporated simultaneously using two independently controlled electron-beam-heated evaporation sources. Copper and cast iron were used as substrates; they were maintained at a bulk temperature of 570 K. From X-ray diffraction studies it was observed that the (111) and (200) interplanar spacings for f.c.c. nickel increased with aluminium content. The presence of a disordered Ni3Al crystallographic structure was observed for an aluminium content exceeding 20 at.% by X-ray diffraction but at 17 at.% Al in transmission electron diffraction. This was due to the size and amount of the Ni3Al domains present. A further increase in aluminium content initiated the formation of disordered b.c.c. NiAl. The variations in hardness showed a close relation to the crystallographic phases existing at different compositions. The appearance of geometrically oriented surface outgrowths between 35 and 50 at%. Al observed in scanning electron microscopy studies is closely related to the formation of b.c.c. NiAl. © 1979.