Acoustic Relaxations in Zirconium-Niobium Alloys

Abstract

Acoustic measurements are reported which were made by the composite resonator technique on poly-crystalline and single-crystal specimens of Zr-Nb alloys (0%-25% Nb). Three distinct thermally activated relaxation peaks have been observed. In the frequency range 80–300 kc/sec, the relaxations occur in the neighborhood of 160°, 40°, and 12°K, with activation energies of 0.3, 0.05, and ∼0.02 eV, respectively. The relaxation which occurs at 12°K has only been observed in Zr-5% Nb. The 160° and 40°K relaxations have been demonstrated to be associated with the β → ω, athermal transformation. An atomic model for the 160°K relaxation process is presented and a tentative suggestion made for the origin of the relaxation at 40°K. No mechanism for the 12°K relaxation is attempted.