STP955: Radiation-Induced Segregation in Light-Ion Bombarded Ni-8% Si

    Packan, N
    Research staff member, and research associate, Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN

    Heatherly, L
    Research staff member, and research associate, Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN

    Kesternich, W
    Research Scientists, Institute for Solid State Research, Jülich Nuclear Research Facility, Jülich,

    Schroeder, H
    Research Scientists, Institute for Solid State Research, Jülich Nuclear Research Facility, Jülich,

    Pages: 11    Published: Jan 1987


    Abstract

    Radiation-induced segregation (RIS) is an important area of current research because of potential detrimental effects including embrittlement. In this work, a quantitative assessment is made of radiation-induced silicon segregation to internal grain boundaries compared with that to the external surfaces. Tension specimens of Ni-8 atomic % Si have been irradiated at 750 K (475°C) with either 7-MeV protons or 28-MeV alpha particles to damage levels of 0.1 to 0.3 dpa. Postirradiation tension testing at 300, 720, or 975 K produces ductile failures with elongations > 15%. However specimens that had implantation of 250 to 1000 atomic ppm He at 975 K (700°C) before irradiation did fracture intergranularly when pulled at 975 K inside a scanning Auger microprobe, thereby exposing grain boundary surfaces for depth profile analysis. After correction for preferential sputtering effects, RIS of silicon to outer surfaces is found to give rise to a strongly enriched surface layer, 20 to 30 nm thick, followed by a shallow depletion zone for the next ∼200 nm, in agreement with previous studies in the literature. By contrast, silicon segregation to fracture-exposed grain faces varies considerably from face to face but generally declines more gradually with little or no depletion zone. Observations of silicon profiles and Ni3Si formation at grain boundaries obtained by analytical transmission electron microscopy (TEM) generally confirm the Auger results.

    Keywords:

    segregation, radiation-induced segregation (RIS), embrittlement, silicon segregation, nickel, helium effects, grain boundaries (segregation), charged particle irradiation


    Paper ID: STP33847S

    Committee/Subcommittee: E10.07

    DOI: 10.1520/STP33847S


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