Recent Progress in Developing and Qualifying Nanostructured Ferritic Alloys for Advanced Fission and Fusion Applications

This article summarizes the recent progress on developing a class of potentially transformational structural materials called nanostructured ferritic alloys, which are leading candidates for advanced fission and fusion energy applications. Here, we focus on Fe-Cr-based ferritic stainless steels containing a very high concentration of Y-Ti-O nano-oxide features that enable a host of outstanding high-temperature properties, along with unique irradiation tolerance and thermal stability. Perhaps most notably, these alloys have an unprecedented capability to manage very high helium concentrations, pertinent to fusion service, in a way that transforms this element from a severe liability to a potential asset. In addition to providing some necessary background, we update progress on: (I) the character of the nanofeatures; (II) some unifying insights on key mechanical properties; (III) a quantitative model for nanofeature coarsening; (IV) recent irradiation experiments of the effects of helium on cavity evolution and void swelling; and (V) a powerful new mechanism controlling the transport, fate, and consequences of helium.