The stress orientation of hydride in zirconium alloys

Abstract

J. C. M. Li's theory of stress orientation of disc shaped precipitates is applied to the problem of stress orientation of hydride in zirconium alloys. It is shown that the stress orientation of the hydride occurs through orientation of the nuclei rather than through preferential growth of stable nuclei, the effect of crystallographic texture is clearly defined, and the experimentally observed dependence on stress is explained. Insufficient experimental data are available to make a quantitative test of the theory for metallurgical conditions in which the hydride is precipitated on both inter- and intra-granular sites in the alloy, but the experimental observations are shown to be consistent throughout. In particular, the susceptibility of quenched and aged Zr/2.5 wt % Nb to stress orientation, compared with the much lower susceptibility of cold worked Zr/2.5 wt % Nb, follows logically from the theory, and the mechanistic basis for the apparent critical stress is demonstrated.