Anisotropic irradiation creep of zircaloy-2

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Abstract
The inherent texture and unique Burgers vector in h.e.p. zircaloy tubing should confer anisotropic creep properties on the material. The results of an experiment designed to measure the anisotropy of irradiation creep using pressurized tubes are analysed in terms of a texture-dependent model based on glide. The predominantly radial texture of the tubes produces a negative axial creep rate following subtraction of the zero-stress irradiation growth. Assuming that the deformation occurs by slip restricted to certain systems whose relative contributions are empirically determined, the model predicts the magnitude and sense of the creep rate to within ∼10%. Experimental evidence that slip processes are operative in irradiation creep is provided by the observation of cleared slip bands in the microstructure. Possible mechanisms considered for slip-band production are either climb-controlled glide or yielding creep modified to include a non-spherical yield function.