STP681

    A Microstructure-Based Constitutive Relation for Dilute Alloys of α-Zirconium

    Published: Jan 1979


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    Abstract

    The microstructural basis for a particular form of constitutive equation relating true stress to true plastic strain in Zircaloy is examined. It is shown that simple physical assumptions about the work-hardening mechanism can lead to an equation of the form τ=τi+Kγn(γ˙/γ˙0)m relating the true stress τ to true plastic strain γ at a constant true strain rate γ˙. The parameters τi, K, n and γ˙0 are dependent on material parameters such as the shear modulus and the Burgers vector of slip dislocations. The strain-rate sensitivity m is shown to be strain dependent in this model. Analysis of experimental data obtained on Zircaloy-4 at two strain rates over a temperature range from 473 to 1073 K demonstrates that the equation provides an excellent fit to experimental data. However, the temperature and strain-rate dependence of the material parameters are not in accordance with the theory. It is concluded that accuracy of fit to stress-strain data cannot be used as a criterion for the validity of a microstructural model and that more accurate microstructural models are required to permit predictions of the variations of phenomenological coefficients with test conditions.

    Keywords:

    Zircaloys, plastic properties, tension tests, stress strain curves, dislocations (materials)


    Author Information:

    Hartley, CS
    University of Florida, Gainesville, Fla.

    Lee, J-J
    University of Florida, Gainesville, Fla.

    Garde, A
    Agronne National Laboratory, Argonne, Ill.

    Chung, HM
    Agronne National Laboratory, Argonne, Ill.

    Kassner, TF
    Agronne National Laboratory, Argonne, Ill.


    Paper ID: STP36689S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP36689S


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