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

    Published: Jan 1979

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    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.


    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.

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP36689S

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