STP1547: Dislocation Bias Calculations in Metals Using a Combined Finite-Element Rate-Theory Approach

    Seif, Dariush
    Dept. of Mechanical Engineering, Univ. of California, Los AngelesLos Angeles, CA

    Ghoniem, Nasr M.
    Dept. of Mechanical Engineering, Univ. of California, Los AngelesLos Angeles, CA

    Pages: 12    Published: Jan 2013


    Abstract

    Void swelling in metals exposed to neutron irradiation has long been known to be enhanced by the preferential absorption of interstitials, rather than vacancies, to dislocations. A common measure of this preference is called the dislocation bias factor and is computed from the ratio of capture efficiencies of dislocations to interstitials and vacancies. Whereas the absorption of interstitials will lead to dislocation climb, the excess vacancies will form voids over time and lead to excessive swelling in the material. In this study, a combined finite-element method (FEM) rate-theory (RT) approach is used to calculate dislocation bias factors in four model bcc (iron, tungsten) and fcc materials (copper, nickel). The flux of point defects to the dislocation core in the model results from the drift term in the diffusion equation. This drift term is a function of the spatially dependent interaction energy between the point defect and the dislocation. One major advantage of this model is the ability to resolve the complex and spatially dependent diffusion pathways of point defects near the dislocation core. Using a previously developed atomistic continuum coupling method, the interaction energies are computed as the inner product between the dipole tensor of the point defect and the strain tensor caused by the dislocation. The bias factors obtained using these methods are compared directly to numerically and analytically obtained values from previous studies and the discrepancies elucidated. The dependence of the bias factors on temperature, dislocation density, and damage dose rate are examined.

    Keywords:

    dislocation bias, capture efficiency, anisotropic diffusion, rate-theory


    Paper ID: STP103987

    Committee/Subcommittee: E10.02

    DOI: 10.1520/STP103987


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