The Effect of Y/Ti Ratio on Oxide Precipitate Evolution in ODS Fe-14 Wt Pct Cr Alloys

Fe-14Cr-1W oxide dispersion strengthened ferritic alloys have excellent mechanical properties at high temperatures due to a high density of thermally stable Y-Ti-O nanoclusters, which are rather stable at high temperature. The aim of this work was to study the evolutions of Y-Ti-O precipitation at high temperature as a function of nominal content of Y, Ti, and O. Different Fe-14Cr alloys were characterized by small-angle neutron scattering technique under magnetic field as well as transmission electron microscopy investigations before and after annealing at 1573 K to 1723 K (1300 °C to 1450 °C). Significant differences are observed depending on the Y/Ti/O ratios. For Ti/Y >1, the coarsening kinetics is low even at 1723 K (1450 °C). For Ti/Y <1, very large size particles are observed after annealing at 1573 K (1300 °C). We have shown that the oxygen content should be strictly controlled to avoid significant coarsening at 1573 K (1300 °C) and above.