Relationships between thermoelectric power (TEP) values and crystallographic texture of zircaloy-4 plates

In zirconium base alloys, Thermoelectric Power (TEP) measurements are known to be sensitive to the concentration of alloying elements, such as iron an d chromium, in solid solution. In this paper, the relationship between the TEP data and the oxygen content of Zy-4, for concentrations ranging from 10 0 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 a hexag onal crystallographic structure) and the TEP data, which is the main object ive of the present paper. To study the relationship between texture and TEP data, a Zy-4 plate heat t reated at three different temperatures and showing three particular crystal lographic textures (Stress-Relieved, Fully Annealed and Beta-Treated metall urgical conditions) has been used. The texture of the samples has been char acterised by x-ray diffraction techniques using pole figures measurements a nd the calculation of the Orientation Distribution Function (ODF). The relationship between TEP data and texture has been performed by using t he Kearns factor, fd, which is an anisotropic coefficient taking into accou nt the volume fraction of <c> axes with respect to the macroscopic referenc e system (Rolling Direction RD, Transverse Direction TD and Normal Directio n ND). On one hand, the TEP measurements are quasi linearly correlated to t he 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 t hat crystallographic orientation effects on TEP could be partly explained b y the interactions of electrons with oxygen atoms located in preferential p lanes (octaedric sites). This study shows that, when the texture is the only varying parameter of th e microstructure, TEP measurement is an easy and fast experimental device w hich can provide a good estimate of the anisotropy of the material. TEP mea surements 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.