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

Abstract

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.

Structure and mechanical properties of Fe–Ni–Zr oxide-dispersion-strengthened (ODS) alloys

“…However, subsequent heat treating of these dissolved additions causes decomposition/interaction to form complex nanoscale oxides greater than 5 nm and/or coherent oxide clusters with diameters less than 2e5 nm. These oxides and oxide clusters are heavily dispersed throughout the Fe matrix and are in part responsible for the high strength and unique properties reported recently [34].…”

Microstructure of HIPed and SPSed 9Cr-ODS steel and its effect on helium bubble formation

“…The size of Y 2 Ti 2 O 7 ranges from a few nanometers to tens of nanometers [14,19e22]. Orthorhombic and hexagonal Y 2 TiO 5 has also been reported but they are not very common [19]; (2) Very small size YeTieO oxides, called nanoclusters (NCs) or nano-oxide features (NFs), have also been reported in many references [1,23,24]. Composition analyses of NCs normally have performed by APT.…”

Influence of Oxygen Supply on Oxide Coarsening During the Internal Oxidation of Two-Phase Fe-Y Alloys

“…[3] This could lead to a bulk-scale production process for nanostructured ferritic alloys (NFA). [4] NFAs are candidate materials for advanced fission and fusion reactor applications and must currently be produced using powder metallurgy processes. [4] There are many challenges to duplicating the unique microstructures of NFAs via internal oxidation in part due to incomplete descriptions of oxidation kinetics of multiphase alloys.…”