Hydride embrittlement in ZIRCALOY-4 plate: Part II. interaction between the tensile stress and the hydride morphology |
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Authors: | J B Bai N JI D Gilbon C Prioul D François |
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Affiliation: | 1. Laboratory MSS/MAT, Ecole Centrale Paris, CNRS URA 850, 92295, Chatenay Malabry, Cedex, France 2. LM3, CNRS URA 1219, ENSAM, 151 Bd de l’H?pital, 75013, Paris, France 3. CEA/DTA/CEREM/DTM/SRMA, C.E.N. Saclay, 91191, Gif s/Yvette Cedex, France
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Abstract: | The effect of an applied tensile stress on the hydrides morphology in ZIRCALOY-4 was studied. To this end, the residual stresses
around the hydride caused by the hydride precipitation was first evaluated. Considering the disability to predict hydride
transformation stresses by ordinary macroscopical mechanical calculation in previous studies, X-ray diffraction (XRD) profile
analysis and transmission electron microscopy (TEM) observations were carried out to quantify the microstructural evolution
in hydrided ZIRCALOY-4. The residual microstrains and microstresses in the matrix and around the hydride were thus estimated.
The big discrepancy between our results and the existing studies were explained by the major self-accomodation of phase transformation
deformation remaining inside the hydrides and the local plastic accommodation of ZIRCALOY-4. In order to study the stress
effect on hydride orientation and to estimate the hydride orientation threshold stresses, hydrogen was introduced into the
specimens under tensile stress. A quantitative technique was used to evaluate the susceptibility to perpendicular hydride
formation under the influence of texture, residual stresses, and externally applied tensile stresses, following an improved
approach that had been first developed by Sauthoff and then applied to Zr-H system by Puls. Both analytical and experimental
results indicate that the threshold stress for producing perpendicular hydrides varies with the microstructural features,
the yield strength, and the residual stresses. |
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