Creep strength of Zircaloy-4 cladding depending on applied stress and annealing temperature

Tube creep tests were conducted on low tin Zircaloy-4 cladding with variations given in final annealing temperatures of 769–893 K, test temperatures of 613–673 K and applied hoop stresses of 90–195 MPa. The enhanced creep rates of low tin Zircaloy-4 by a factor of 2 compared with standard Zicaloy-4 were observed mainly due to reduced tin content. It was found that the creep parameters had a considerable stress dependency, that is, the activation energy and stress exponent decreased with stress increment. The plausible contribution of Coble creep to low-temperature-annealed Zircaloys at a lower stress range is discussed based on the determined creep parameters, microstructure and texture to explain the observed stress dependency.