Stability of non-stoichiometric clusters in the MA957 ODS ferrtic alloy

Sakasegawa, Hideo   ; Legendre, F.*; Boulanger, L.*; Brocq, M.*; Chaffron, L.*; Cozzika, T.*; Malaplate, J.*; Henry, J.*; de Carlan, Y.*

In our past work, the commercial ferrtic Oxide Dispersion Strengthened (ODS) alloy MA957 had at least two types of nanometer-sized oxide particles: non-stoichiometric Y-, Ti-, O-enriched clusters and YTiO particles. The size of the non-stoichiometric clusters was much smaller than that of YTiO particles and it was confirmed that the non-stoichiometric clusters possibly dominate the oxide dispersion strengthening. Therefore, this study dealt with the stability and evolution mechanisms of non-stoichiometric nanoclusters after the annealing (1473K 1h). This annealing condition was determined considering the actual condition of consolidation processes. After the annealing, most non-stoichiometric Y-, Ti-, O-enriched clusters were stable, but some clusters became YTiO particles with increasing size. The diffusion of yttrium had an important role for the evolution of these oxides.