Creep of zirconium and zirconium alloys

Cumulative zirconium and zirconium alloy creep data over a broad range of stresses (0.1 to 115 MPa) and temperatures (300 °C to 850 °C) were analyzed based on an extensive literature review and experiments. Zirconium obeys traditional power-law creep with a stress exponent of approximately 6.4 over stain rates and temperatures usually associated with the conventional “five-power-law” regime. The measured activation energies for creep correlated with the activation energies for zirconium self-diffusion. Thus, dislocation climb, rather than the often assumed glide mechanism, appears to be rate controlling. The common zirconium alloys (i. e., Zircaloys) have higher creep strength than zirconium. The stress exponents of the creep data in the five-power-law regime were determined to be 4.8 and 5.0 for Zircaloy-2 and Zircaloy-4, respectively. The creep strength of irradiated Zircaloy appears to increase relative to unirradiated material. It was found that the creep behavior of zirconium was not sensitive to oxygen in the environment over the temperature range examined.