Creep of Zirconium and Zirconium Alloys

Controlling mechanisms for creep of zirconium and zirconium alloys continue to be debated. In previous studies, the authors analyzed cumulative zirconium and zirconium alloy creep data over a broad range of stresses (0.1–115 MPa) and temperatures (300–850 °C) based on a 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 stress exponents of the creep data in the five-power-law regime for Zircaloy-2 and Zircaloy-4 were determined to be 4.8 and 5.0, respectively. Further advances in the understanding of the controlling mechanisms for zirconium and zirconium alloys will be presented based on a review of the literature over the past decade.