Transformation de phase dans l'aluminium induite par implantation ionique de nickel à haute énergie

Abstract
Implantation of Ni into a pure Al target leads to the formation of amorphous zones. Their formation is studied by transmission electron microscopy (TEM). The present results were obtained in samples implanted with ions having energies between 22 and 40 MeV and fluences between 1.68x10¹⁵ and 2.5x10¹⁷ ions/cm². In order to observe the profile of the ion implantation in the TEM, cross-sectional samples were thinned with a specially modified ion bombardement. Measurements of the atomic concentration have been carried out with energy dispersive spectroscopy (EDS). In spite of the Ni concentration (up to 3 at. %) in the implanted layer, there is no observable nuclei of the Al₃Ni phase after implantation at 120 K and room temperature. In contrary, amorphous zones with a diameter of about 10 nm are present together with a high density of dislocation loops and dislocations. The Ni concentration in the amorphous zones is about 25 at. %. An implantation conducted at 520 K shows only crystalline precipitates of Al₃Ni. We conclude that the Ni implanted in Al agglomerates in zones having composition identical to that of the Al₃Ni phase.