BIAXIAL CREEP OF TEXTURED ZIRCALOY .1. EXPERIMENTAL AND PHENOMENOLOGICAL DESCRIPTIONS

Creep of Zircaloy-4 was studied using biaxially loaded tubes at 673 K. Pronounced creep anisotropy is attributed to the presence of strong preferred orientations. Stress and temperature dependences for steady state creep were determined from closed-end internal pressurization tests. The derived activation energy and area suggest that the climb of edge dislocations is the rate-controlling mechanism for creep in Zircaloy. A single relationship derived correlates the temperature and stress dependence of primary creep behavior over the range of experimental investigation. Anisotropic creep behavior as a function of loading state is modelled using R. Hill's anisotropic formulation modified for constant levels of creep potential. This approach is successful for both cold-worked stress-relieved materials and partially recrystallized materials.