STP611

    Effects of Neutron Irradiation on Microstructure and Mechanical Properties of Nimonic PE-16

    Published: Jan 1976


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    Abstract

    Specimens of Nimonic PE-16, a γ'-hardened austenitic alloy, were irradiated in the Experimental Breeder Reactor-II (EBR-II) in order to determine the effect of neutron irradiation on the microstructure and mechanical properties. Specimens with two different aging treatments were irradiated at temperatures ranging from 650 to 823 K and fluences ranging from 1.2 × 1026 neutrons (n)/m2 to 4.0 × 1026 n/m2. The aging treatments were: (A) 2h at 1313 K + 2 h at 1073 K + 16 h at 973 K; and (B) 4 h at 1313 K + 1 h at 1173 K + 8 h at 1023 K. Postirradiation transmission electron microscopy (TEM) revealed the presence of voids in all irradiated specimens. No difference in the fluence dependence of swelling at an irradiation temperature of 773 K was observed between the specimens with Preirradiation Treatment A and the specimens with Preirradiation Treatment B. In contrast, the temperature dependence of swelling appears to be sensitive to the particular preirradiation aging treatment used. TEM also shows that existing precipitates coarsen slightly during irradiation and that precipitation of γ'-precipitates occurs on irradiation-produced dislocation loops and voids.

    Specimens irradiated at 773 K were tensile tested at 683, 773, 873, and 973 K. There is no significant difference in postirradiation mechanical properties between the two preirradition heat treatments. There is a large increase in yield strength after irradiation, which is consistent with the observed changes in microstructure. The ductility decreases as the test temperature increases. The low ductilities observed at the higher test temperatures are associated with a tendency for intergranular fracture. Auger spectroscopy of fracture surfaces on a specimen fractured at 823 to 873 K in the Auger chamber indicates that the concentrations of phosphorus and sulfur are a factor of two or three higher, and that the concentrations of iron and chromium are a factor of two lower, on surfaces of grain boundary fracture than on surfaces resulting from ductile fracture within the same specimen. There is also an enrichment of nickel at grain boundaries. In addition, helium release was observed at the time of fracture.

    Keywords:

    radiation, neutron irradiation, nickel-based austenitic alloys, precipitation hardening, radiation damage, mechanical properties, swelling, voids, Auger spectroscopy, transmission electron microscopy, precipitation


    Author Information:

    Sklad, PS
    Research staff members, Oak Ridge National Laboratory, Metals and Ceramics Division, Radiation Effects and Microstructural Analysis Group, Oak Ridge, Tenn.

    Clausing, RE
    Research staff members, Oak Ridge National Laboratory, Metals and Ceramics Division, Radiation Effects and Microstructural Analysis Group, Oak Ridge, Tenn.

    Bloom, EE
    Research staff members, Oak Ridge National Laboratory, Metals and Ceramics Division, Radiation Effects and Microstructural Analysis Group, Oak Ridge, Tenn.


    Paper ID: STP38045S

    Committee/Subcommittee: E10.07

    DOI: 10.1520/STP38045S


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