Feasibility of using Y₂Ti₂O₇ nanoparticles to fabricate high strength oxide dispersion strengthened Fe-Cr-Al steels

Addition of Al can improve the corrosion resistance of oxide dispersion strengthened (ODS) steels. However, Al reacts with Y2O3 to form large Y-Al-O particles in the steels and deteriorates their mechanical properties. Herein, we successfully prepared Y2Ti2O7 nanoparticles (NPs) by the combination of hydrogen plasma-metal reaction (HPMR) and annealing. Y2Ti2O7 NPs with contents of 0.2 or 0.6 wt.% were then added into the Fe-14Cr-3Al-2W-0.35Ti (wt.%) steel to substitute the conventional Y2O3 NPs by mechanical alloying (MA). The Y2Ti2O7 NPs transformed into amorphous-like structure after 96 h MA. They crystallized with a fine size of 7.4±3.7 nm and shared a semi-coherent interface with the matrix after hot isostatic pressing (HIP) of the ODS steel with 0.6 wt.% Y2Ti2O7. With the increasing Y2Ti2O7 content from 0.2 to 0.6 wt.%, the tensile strength of the ODS steel increased from 1238 to 1296 MPa, which was much higher than that (949 MPa) of the ODS steel added with Y2O3. The remarkably improved mechanical properties of the Al-containing ODS steels were attributed to the increasing number density of Y2Ti2O7 nanoprecipitates. Our work demonstrates a novel route to fabricate high performance ODS steels with both high mechanical strength and good corrosion resistance.