Investigation of the Zr-2,5%Nb alloy structure by ultrasonic spectral analysis

In the present paper, we used the ultrasonic scattering properties as a tool for micro-structural evaluation of metals. The cold-worked Zr-2.5%Nb alloy is used for the pressure tubes in CANDU nuclear reactors. This material has developed a strong texture due to the limited slip system during extrusion process, leading to anisotropic properties. For this reason, it is very important to be able to evaluate its microstructure. The frequency dependence of attenuation coefficient in Zr-2.5%Nb alloy was measured and the scattering coefficient was calculated. The experimental data were fitted to the Rayleigh region scattering. The experimental results obtained with ultrasonic spectroscopy, in grain size evaluation, has been compared with those obtained by metallographic analysis (ASTM E112). The good agreement between them indicates that this method can be used in non-destructive investigation of grain size for nuclear materials. The inverse problem is: by using the determined grain size we can evaluate the elastic coefficients. (authors)