STP870

    Microsegregation Observed in Fe-35.5Ni-7.5Cr Irradiated in EBR-II

    Published: Jan 1985


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    Abstract

    In another recent study of the compositional dependence of swelling in annealed iron-nickel-chromium alloys, it was found that some annealed alloys densified during irradiation. No precipitate phases were observed to form, however. At 593°C, one alloy, Fe-35.5Ni-7.5Cr, which was particularly resistant to swelling, increased in density 0.9% at 7.6 × 1022 neutrons (n)/cm2 (E > 0.1 MeV).

    Examination by energy dispersive X-ray analysis revealed that substantial oscillations occur in the nickel content of the alloy, varying from 25 to 53% about the nominal level of 35.5%. These oscillations exhibit a period of ∼200 nm. Regions enriched in nickel are depleted in chromium and iron, and the reverse is true in regions of low nickel content. This spinodal-like process produces a net densification and also appears to eventually destroy the swelling resistance of the alloy. Once voids form in the nickel-poor chromium-rich regions, further segregation of nickel to void surfaces is expected to accelerate the loss of swelling resistance.

    Keywords:

    radiation, austenitic alloys, neutron irradiation, compositional modulation, densification, order-disorder, spinodal, swelling


    Author Information:

    Brager, HR
    Senior research engineer and fellow scientist, Hanford Engineering Development Laboratory, Richland, WA

    Garner, FA
    Senior research engineer and fellow scientist, Hanford Engineering Development Laboratory, Richland, WA


    Paper ID: STP37358S

    Committee/Subcommittee: E10.08

    DOI: 10.1520/STP37358S


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