APT characterization and modeling of irradiation-induced Nb-rich nanoclustering in Zr-1.0%Nb alloys

Recent development of Zr-based alloys containing Nb solutes have demonstrated promising improvements in corrosion resistance and reduced irradiation growth, particularly when irradiation-induced Nb-rich nanoclusters are present and inhibit (c) loop formation. In this study, a Zr-1.0%Nb alloy is irradiated with either Kr2+ ions or neutrons to 5 dpa at 310 degrees C. Using atom probe tomography, radiation-induced Nb-rich nanoclusters and a corresponding reduction of Nb matrix composition from 0.40 at% to 0.26 at% and 0.34 at% is characterized following each irradiation, respectively, suggesting that matrix solutes coalesce to form nanoclusters. Irradiation with Kr2+ ions induces nanoclusters that are larger and denser than those following neutron irradiation. Utilization of a simple rate-theory nanocluster evolution model demonstrates high sensitivity to the solute migration, vacancy formation, and vacancy migration energies directly influencing radiation-enhanced mobility of solutes, enabling exploration of irradiation temperature effects and potential differences in nanocluster evolution for different solutes or alloy systems.