Temperature effect of dynamic anisotropic elastic constants of Zr–2.5Nb pressure tube by resonant ultrasound spectroscopy

Dynamic anisotropic elastic constants of CANDU Zr–2.5Nb pressure tube materials were determined by high temperature resonant ultrasound spectroscopy (RUS). The resonance frequencies were measured using a couple of alumina waveguides and wide-band ultrasonic transducers in a small furnace. The rectangular parallelepiped specimens were fabricated along with the longitudinal, radial and transverse direction of the pressure tube. The initial estimates for RUS were obtained from the orientation distribution function by X-ray pole figure and elastic stiffness of single crystal zirconium. A nine elastic stiffness tensor for orthotropic symmetry was determined in the range of room temperature ∼500 °C. As the temperature increases, the elastic constant tensor, cij gradually decreases. Higher elastic constants along the transverse direction compared to those along the longitudinal or radial direction are similar to the case of Youngʹs modulus or shear modulus. A crossing of elastic constants along the longitudinal direction and radial direction was observed near 120–150 °C. This fact could correlate to the crossing characteristics of c44 and c66 of a zirconium single crystal in the temperature range.