Influences of adding Y2Ti2O7 and HfH1.98 nanoparticles on the microstructure and mechanical properties of oxide dispersion strengthen steels

Adding Y2O3 will make Al-containing oxide dispersion strengthened (ODS) steels produce coarse Y-Al-O particles, which deteriorates their mechanical properties. Herein, Y2Ti2O7 nanoparticles and Hf hydride nanoparticles (NPs) were successfully prepared by hydrogen plasma-metal reaction (HPMR) method and added together in the Fe-Cr-Al ODS steel to replace the traditional Y2O3 NPs. The microstructure of matrix and oxide in ODS steels has been characterized by scanning transmission electron microscopy (STEM) and high resolution transmission electron microscopy (HRTEM). The oxide NPs in FHYT-0.6 (Fe-14Cr-4.5Al-2 W-0.35HfH1.98–0.6Y2Ti2O7, wt%) are made of Y2Ti2O7 (semi-coherent with the matrix and about 10 nm) and HfO2 (incoherent with the matrix and about 26 nm). The size of oxide dispersoid in FHYT-0.6 is reduced to 8.8 nm and the number density is greatly increased to 9.4 × 1023 m−3 compared with FTYT-0.6 (Fe-14Cr-4.5Al-2 W-0.35Ti-0.6Y2Ti2O7, wt%) and FTY-0.6 (Fe-14Cr-4.5Al-2 W-0.35Ti-0.6Y2O3, wt%). The tensile strength at room temperature of FHYT-0.6 is 1194 MPa, which is 24.1 and 14.1% higher than the FTY-0.6 and FTYT-0.6, respectively. Our work has proved that the mechanical properties of the alloy can be significantly improved by adding Y2Ti2O7 and HfH1.98 NPs, which provides a new idea for manufacturing high-performance ODS steels.