title: Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys.
abstract: A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. Here we report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.
authors.affiliation: Key laboratory of Superlight Materials and Surface technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin 150001, China.
authors.forename: Z W
authors.initials: ZW
authors.lastname: Zhang
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: L
authors.initials: L
authors.lastname: Yao
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong.
authors.forename: X-L
authors.initials: XL
authors.lastname: Wang
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: M K
authors.initials: MK
authors.lastname: Miller