SANS study of microstructural evolution in oxide strengthened EUROFER steel after heat treatments

Oxide dispersion strengthened (ODS) reduced activation ferritic/martensitic steels are being developed for structural applications in future fusion reactors since they would allow consistently increasing the operation temperature The 9%CrWVTa Eurofer-97 steel has been selected as a base material strengthened by Y2O3 contents of 0.3 and 0.5 wt% and produced in a powdermetallurgical route by mechanical alloying and hot isostatic pressing (HIP). The mechanical properties are strongly correlated with Y2O3 particle average size and spatial distribution, therefore small-angle neutron scattering (SANS) is quite useful to investigate how these evolve in the course of the production steps. Solid polycrystalline samples as well as mechanically alloyed powders have been investigated after thermal treatments thus simulating the HIP conditions. The obtained SANS results show that annealing at high temperature results in a redistribution of scattering centres sizes, which might be attributed to the growth of small Yttria particles and possibly of larger carbides.