J. Phys. IV France 10 (2000) Pr10-203-Pr10-209
Relationships between thermoelectric power (TEP) values and crystallographic texture of zircaloy-4 platesJ.L. Béchade, J.C. Brachet, J. Pelé and T. Guilbert
CEA-CEREM, Service de Recherches Métallurgiques Appliquées, CEA Saclay, 91191 Gif-sur-Yvette cedex, France
In zirconium base alloys, Thermoelectric Power (TEP) measurements are known to be sensitive to the concentration of alloying elements, such as iron and chromium, in solid solution. In this paper, the relationship between the TEP data and the oxygen content of Zy-4, for concentrations ranging from 100 to 4000 ppm, has been established, not only to link the oxygen content to the TEP but also to separate this effect from the relationship established between the texture of polycrystalline Zircaloy-4 samples (with an α hexagonal crystallographic structure) and the TEP data, which is the main objective of the present paper. To study the relationship between texture and TEP data, a Zy-4 plate heat treated at three different temperatures and showing three particular crystallographic textures (Stress-Relieved, Fully Annealed and Beta-Treated metallurgical conditions) has been used. The texture of the samples has been characterised by x-ray diffraction techniques using pole figures measurements and the calculation of the Orientation Distribution Function (ODF). The relationship between TEP data and texture has been performed by using the Kearns factor, fd, which is an anisotropic coefficient taking into account the volume fraction of <c> axes with respect to the macroscopic reference system (Rolling Direction RD, Transverse Direction TD and Normal Direction ND). On one hand, the TEP measurements are quasi linearly correlated to the Kearns anisotropic coefficients fd, on the other hand, the study of the influence of oxygen content on TEP has shown that the texture effect seems to be reduced when the oxygen content is low. One can make the assumption that crystallographic orientation effects on TEP could be partly explained by the interactions of electrons with oxygen atoms located in preferential planes (octaedric sites). This study shows that, when the texture is the only varying parameter of the microstructure, TEP measurement is an easy and fast experimental device which can provide a good estimate of the anisotropy of the material. TEP measurements can also give a fairly local information of the texture. Finally, it is shown that this technique can be applied to estimate the texture of Zircaloy-4 tubes.
© EDP Sciences 2000