Perspective steels for generation IV and fusion reactors

In this study we focus on the F/M steel Eurofer, the European candidate material for the future fusion reactor and for the strengthening we consider oxides of yttrium. The oxides of yttrium and complex yttrium titanium oxides reinforce the material by forming more or less stable obstacles to dislocations, and by promoting grain refinement by pinning grain boundaries. It appears that part of the yttrium titanium oxides particles dissolves from about 600 grad C while pure Yttria particles are stable at least to 1000 grad C in the steel. The aims of this study are the following: 1) Prove the positive effect of strengthening by yttrium oxides. 2) Measure the hardness of base Eurofer and ODS version by Vickers hardness test (HV). 3) Investigate the behaviour of steels at different annealing temperatures and the changes in strength. 4) Assess defects in microstructure by Coincidence Doppler Broadening (CDB) and Positron Annihilation Lifetime Spectroscopy (PALS) at chosen annealing temperatures. (authors)