High resolution microstructural studies of the evolution of nano-scale, yttrium-rich oxides in ODS steels subjected to ball milling, selective laser melting or friction stir welding

Coarse-grained ferritic Oxide Dispersion Strengthened (ODS) FeCrAlY alloys were initially developed for use in high temperature environments due to their excellent creep strength and oxidation resistance. More recently, ODS materials capable of forming protective α-alumina scales have attracted increasing interest for nuclear applications, due to their potential corrosion resistance in super-critical water and liquid metal environments. However, there is still controversy about how and when the fine dispersoids form; and whether they are transformed during fabrication processes. In this paper high spatial resolution electron microscopy is used to monitor the evolution of the dispersoids under different conditions including: heat treatment of as-milled powder, selective laser melting and friction stir welding.