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 0.6wt.% 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 96h MA. They crystallized with a fine size of 7.4±3.7nm and shared a semi-coherent interface with the matrix after hot isostatic pressing (HIP) of the ODS steel with 0.6wt.% Y₂Ti₂O₇. With the increasing Y₂Ti₂O₇ content from 0.2 to 0.6wt.%, the tensile strength of the ODS steel increased from 1238 to 1296MPa, which was much higher than that (949MPa) 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.