Irradiation damage of oxide dispersion strengthened steels for nuclear applications

Reduced activation ferritic steels may have important applications as structural components in future designs of fusion reactor. The high-temperature mechanical properties of these steels are greatly improved by the addition of nanoscale oxide particles. The properties of these oxide dispersion strengthened (ODS) steels are primarily dependent on the particle distribution and character. Therefore, to understand these materials the oxide particles need careful characterisation. Due to the small size of the oxide particles (1-5 nm) the advanced techniques of atom probe tomography and transmission electron microscopy must be used.
Working with collaborators at the Indira Gandhi Centre for Atomic Research in India model alloys ODS steel have been produced. These model alloys have a well-known composition and processing route making them ideal for a study of the fundamental behaviour of the oxide particles.

The influence of displacement damage on these particles is a subject of great interest. To simulate neutron damage, ion irradiation at various temperatures can be used as an analogue. Because of the shallow depth (1 um) of the ion irradiation, sample preparation must performed using focused ion beam techniques.

So far in this project, over one hundred atom probe experiments have been performed to characterise the as-received material as well as ion irradiated samples. Further ion irradiation experiments are planned to investigate the response of the oxide particles to irradiation at low temperatures.