Structural analysis of amorphous NixTi1−x alloys (x = 0.3–.07), obtained by vapor deposition, ion implantation and electron irradiation, has been made by electron diffraction techniques. Radial distribution functions (RDF) were derived from microdensitometer traces of diffraction patterns. From a simple fit routine, used to account for the decreasing width and position of the first RDF peak as the Ni concentration increases, it has been deduced that this first peak is the result of an overlap of two atomic coordination shells containing approximately 12 and 6 atoms, respectively; these coordination numbers are typical of a close packed structure. This may suggest that such atomic arrangements exist in the form of short range order in the amorphous structure. No major differences, in terms of peak positions and coordination numbers, were found between the structures of the amorphous NiTi alloys obtained by vapor deposition ion implatation and electron irradiation.

Ion-beam-induced atomic mixing of Ti/Ni and amorphous TiNi/Ni brought about by a 300 keV krypton beam is studied by Rutherford backscattering analysis. It is shown that a predeposited thin amorphous layer of NiTi between titanium and nickel does not affect the mixing of the NiTi couple. Mixing experiments carried out with the bilayered sample (amorphous TiNi/Ni) show that the effective irradiation-enhanced diffusion of nickel into the amorphous alloy NiTi is very large. In all the experiments, the nickel concentration CNi in the amorphous alloy tends to the value 0.6.

The amorphous nature of a-Ti 60 Si 40 formed by interdiffusion of sputtered TiSi multilayers has been confirmed by the calculation of a radial distribution function (RDF) from scattering patterns obtained by electron diffraction. This material shows the characteristics of an amorphous metallic alloy with a coordination number of 11.4. The atomic pair distribution function shows some similarity to the crystalline silicide closest to it in composition — Ti 5 Si 4 . The likely presence of chemical short-range order in the alloy is consistent with the driving force for the formation of the amorphous state by interdiffusion in the TiSi system, which is the formation of TiSi bonds.

In previous work it has been shown that the N+ implanted NiTi alloy surface consists of crystalline TiN precipitates embedded in an amorphous structure. This surface modification considerably reduces the friction coefficient and dramatically increases wear resistance. A coating of this type on stainless steel has been prepared using a high-energy ion beam assisted deposition (IBAD) technique. TEM, SIMS and XPS analyses show that sputtering of an Ni49Ti51 target with 1.5 keV N+ ions leads to an amorphous N153Yi47 film with a high content of nitrogen and containing small TiN precipitates (5 nm). When the growing film is simultaneously bombarded with a 160 keV Ar+ beam the precipitates are bigger (10 nm) and the coating-substrate interface is mixed over a thickness of 200 nm. The wear resistance of these coatings deposited on stainless steel 304L is excellent: this is explained in terms of the amorphous structure, fine precipitates created during ion-beam assisted deposition and the diffuse interface.

Ni+ implantation-induced amorphization of NixTi1−x (0.3 ⩽ x ⩽ 0.7) alloys, vs. the temperature, is studied by transmission electron microscopy. Two conflicting processes are shown to occur: ballistic disordering competes with a close pair recombination process (with a low activation energy of approximately 0.03 eV) in the cascades at low temperatures, and with an irradiation-enhanced interstitial mobility (activation energy approximately 0.6 eV) at higher temperatures (beyond 250 K). Nitride precipitation has been observed in N+-implanted Ni50Ti50 alloys. These precipitates, embedded in the amorphous layer, are oriented at low temperature (77 K) and high temperature (473 K) and disoriented around room temperature (293 and 373 K). It is suggested that this orientation occurs when the first epitaxial precipitates nucleate in the crystalline substrate before the amorphization.

Ion-beam-induced atomic mixing of the TiNi system brought about by a 300 keV krypton beam is studied by Rutherford backscattering spectrometric analysis. Samples are as follows: 1.(1) thin markers (30 Å thick) of nickel in a titanium matrix and titanium in a nickel matrix;2.(2) bilayers of nickel (450 Å thick on top) and titanium (1500 Å) electron gun evaporated on a superficially oxidized silicon wafer;3.(3) a thin layer (100 Å thick) of Ni/50 at.% Ti electron gun co-evaporated sandwiched between 450 Å of nickel on top and 1500 Å of titanium.