Developing a novel ODS steel to tailor mechanical properties and microstructure by co-adding VN and Y2O3 powders

• A new ODS steel with the addition of VN and Y 2 O 3 powders was prepared and compared with steels adding only VN or Y 2 O 3 powder. • After the addition of VN and Y 2 O 3 powders in steel together, the V-N-rich Y 2 O 3 precipitates with a finer size and higher number density were formed. • Finer grains with an average size of 0.55 µm and more dislocations with a density of 2.03 × 10 14 m −2 were found in the novel steel. • Significant increase in tensile strength of the new steel without loss of elongation owing to optimized microstructure by adding VN and Y 2 O 3 powders together. To enhance the high-temperature performance and extend the upper service temperature of oxide dispersion strengthened (ODS) steels for fusion reactor applications, a novel 9Cr-ODS steel was designed by co-adding 0.2 wt% VN and 0.35 wt% Y 2 O 3 powders during mechanical alloying. This synergistic design strategy aims to combine the benefits of MX-type nitrides and nano-oxides. For comparison, steels with individual additions of VN or Y 2 O 3 were also fabricated. All three steels exhibited ultra-fine microstructures with submicron grain sizes, high dislocation densities, and a dense dispersion of nanoparticles. The steel with VN powder alone showed excellent ductility at 700 °C (∼40 % elongation), while the steel with Y 2 O 3 powder alone achieved superior strength through effective dispersion strengthening. Remarkably, the co-addition of VN and Y 2 O 3 powders led to the formation of V-N-rich Y 2 O 3 composite nanoparticles with the smallest average size (∼6.4 nm) and highest number density (∼7.9 × 10 22 m −3 ), resulting in a significant enhancement in tensile strength without compromising ductility. This strategy offers a promising route to tailor both strength and ductility in advanced ODS steels, providing a robust framework for designing nuclear structural materials with superior high-temperature performance and radiation resistance.