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In order to investigate the influence of Zr addition on the mechanical properties of oxide dispersion strengthened(ODS)steels,tow contrastive compositions of Fe-14Cr-1.5W-0.3Ti-0.45Y2O3 and Fe-14Cr-1.5W-0.3Ti-0.45Y2O3-1Zr were fabricated by mechanical milling and hot isostatic pressing(HIP)sintering.The TEM analysis indicated that the dispersion morphology(about 20~35nm)and coherency of the oxide nanoparticles in ODS steels with Zr addition were significantly improved relative to the one without Zr addition by reason of the formation of smaller Y-Zr-O particles.Zr contained ODS steels also have more excellent mechanical properties with higher yield strength(12.5%),ultimate tensile strength(5.2%)and uniform elongation(26.3%).The strengthening mechanism was studied by in-situ TEM deformation and it suggested that the dominant particle-dislocation interactions mechanism in ODS steel was Orowan looping mechanism(particle size d ≥ 2.5nm).Equally distributed and smaller sized nanoparticles improved the CRSS needed by dislocations to bypass the particles.