Semiconducting characteristics of oxide film on pure Zr, Zr-Sn binary alloy, and Zr-Sn-X (X: Fe, Ni, or Cr) ternary alloy were evaluated by a photo-electrochemical method to study the effects of alloying elements on the oxidation mechanism of Zr alloy in a boiling water reactor (BWR) environment. Oxide films of the alloys showed the characteristics of an n-type semiconductor. Maximum photocurrent (Imax) was generated by an illumination of monochromatic light with a photon energy of 5 to 6 eV (i.e., the band gap energy of the Zr oxide semiconductor was 5 to 6 eV). Higher corrosion-resistant alloys showed a lower value of Imax. Maximum photocurrent decreased by an addition of Fe, Ni, or Cr, notably Fe or Ni, to Zr-Sn alloy. By repetition of cold-working and α-annealing subsequent to β-quenching, Imax increased. Such changes of Imax caused by changes in alloy chemical composition and material processing, were explained by the valence theory of oxide semiconductors (i.e., the decrease of Imax was considered to result from the increase of holes in the oxides due to the substitution of divalent cations (Ni2+) and trivalent cations (Fe3+, Cr3+ ) at Zr4+ cation sites). From these results, the effects of alloying elements on the oxygen vacancy structure of the surface oxide were believed to play a major role in controlling the corrosion resistance of zirconium alloys.
Various combinations of biaxial stress were applied on five batches of recrystallized zircaloy-2 fuel cladding tubes with different textures ; elongation in both axial and circumferential directions of the specimen was measured continuously up to 5% plastic deformation.T h e anisotropic theory of plasticity proposed by Hill was applied t o t h e resulting data, and anisotropy constants were obtained through the two media of plastic strain loci and plastic strain ratios. Comparison of t h e results obtained with the two methods proved that t h e plastic strain loci provide d a t a that a r e more effective in predicting quantitatively the plastic deformation behavior of the zircaloy-2 tubes. T h e anisotropy constants change their value with progress of plastic deformation, and judicious application of t h e effective stress and effective strain obtained on anisotropic materials will permit the relationship between stress and strain under various biaxialities of stresses t o be approximated by t h e work hardening law.T h e test specimens used in t h e plastic deformation experiments were then stressed t o fracture under the s a m e combination of biaxial stress as i n the proceeding experiments, and t h e deformation in the fractured part was measured. T h e result proved t h a t t h e tilt angle of the c-axis which serves a s the index of texture is related to fracture ductility under biaxial stress. Based on this relationship, it was concluded that material with a tilt angle ranging from 10" t o 15" is the most suitable for fuel cladding tubes, from t h e viewpoint of fracture ductility, at least in the case of unirradiated material.
No abstract
Various combinations of biaxial stress were applied on five batches of recrystallized zircaloy-2 fuel cladding tubes with different textures ; elongation in both axial and circumferential directions of the specimen was measured continuously up to 5% plastic deformation.T h e anisotropic theory of plasticity proposed by Hill was applied t o t h e resulting data, and anisotropy constants were obtained through the two media of plastic strain loci and plastic strain ratios. Comparison of t h e results obtained with the two methods proved that t h e plastic strain loci provide d a t a that a r e more effective in predicting quantitatively the plastic deformation behavior of the zircaloy-2 tubes. T h e anisotropy constants change their value with progress of plastic deformation, and judicious application of t h e effective stress and effective strain obtained on anisotropic materials will permit the relationship between stress and strain under various biaxialities of stresses t o be approximated by t h e work hardening law.T h e test specimens used in t h e plastic deformation experiments were then stressed t o fracture under the s a m e combination of biaxial stress as i n the proceeding experiments, and t h e deformation in the fractured part was measured. T h e result proved t h a t t h e tilt angle of the c-axis which serves a s the index of texture is related to fracture ductility under biaxial stress. Based on this relationship, it was concluded that material with a tilt angle ranging from 10" t o 15" is the most suitable for fuel cladding tubes, from t h e viewpoint of fracture ductility, at least in the case of unirradiated material.
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