STP1295: Evolution of Microstructure in Zirconium Alloys During Irradiation

    Griffiths, M
    Staff scientist, Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario

    Mecke, JF
    Technologists, Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario

    Winegar, JE
    Technologists, Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario

    Pages: 23    Published: Jan 1996


    Abstract

    X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to characterize microstructural and microchemical changes produced by neutron irradiation in zirconium and zirconium alloys. Zircaloy-2, Zircaloy-4, and Zr-2.5Nb alloys with differing metallurgical states have been analyzed after irradiation for neutron fluences up to 25 × 1025 n.m-2 (E > 1 MeV) for a range of temperatures between 330 and 580 K.

    Irradiation modifies the dislocation structure through nucleation and growth of dislocation loops and, for cold-worked materials in particular, climb of existing network dislocations. In general, the a-type dislocation structure tends to saturate at low fluences (< 1 × 1025 n.m-2). The c-component dislocation structure, however, may evolve over long periods of irradiation (for fluences >10 × 1025 n.m-2 in some cases).

    The phase structure is also modified by irradiation. The common alloying/impurity elements, Fe, Cr, and Ni, are relatively insoluble in the α-phase but are dispersed into the α-phase during irradiation irrespective of the state of the phase initially containing these elements, i.e., metastable β-phase or stable intermetallic precipitate. The stable intermetallic particles may undergo structural changes dependent on their composition and the temperature. For the metastable dual-phase α/β-alloys (Zr-2.5Nb alloy), the β-phase structure is modified during irradiation, but the change is complex, being a combination of thermal decomposition and radiation-induced mixing.

    Keywords:

    zirconium, niobium, Zircaloy, zirconium alloys, microstructure, microchemistry, neutron irradiation, radiation damage, dislocation density, lattice parameters


    Paper ID: STP16191S

    Committee/Subcommittee: B10.01

    DOI: 10.1520/STP16191S


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