In situ TEM thermal annealing of high purity Fe10wt%Cr alloy thin foils implanted with Ti and O ions

Abstract

ODS steels are ferritic-martensitic steels reinforced with (Y,Ti) oxide dispersions to enhance the creep and radiation resistance at elevated temperatures. Their conventional fabrication is achieved by ball milling followed by high-temperature consolidation. An alternative approach of ion beam synthesis has been suggested recently to study the early precipitation stages of oxide nanoparticles. To clarify the details of Ti-based oxide nanoparticle precipitation, Ti+ and O+ ions were implanted into high-purity Fe-10 wt%Cr thin foils at room temperature and subjected to thermal annealing. Nano-size oxide particles and larger surface oxide islands with pronounced Cr enrichment were observed after in situ Transmission Electron Microscopy (TEM) annealing at 600 °C and were identified as a mixed iron-chromium spinel. The features observed after ex situ annealing at 800 °C were also identified as iron-chromium oxide, but with a certain titanium enrichment. The observations thus suggest that titanium plays no major role in the early stages of oxide precipitation.