Microstructure and mechanical properties of an ODS ferritic steel with very low Cr content

Abstract An ultra-low Cr oxide dispersion strengthened (ODS) steel with the composition of Fe-5Cr-4.5Al-0.6Zr (hereinafter abbreviated as 5CrAlZr ODS steel) were proposed and manufactured via mechanical alloying (MA) and hot isostatic pressing (HIP), followed by hot forging treatment. TEM results indicate that a large amount of fine δ-Y4Zr3O12 particles were formed within the grains and along the grain boundary, additionally, Y6ZrO11 and Al2Y4O9 nano-particles with larger size were also detected. The mean particles diameter ( d p ), the mean inter-particle spacing (λ) and number density ( n v ) of the nano-oxide particles in the 5CrAlZr ODS steel are about 10 nm, 80 nm and 1.23 × 1022 /m3, respectively. The room temperature ultimate tensile strength (UTS) and the total elongation (TE) of the fabricated 5CrAlZr ODS steel are 875 MPa and 21%, respectively, which are higher than those of traditional 5Cr-2W-0.24V steels. The UTS and TE of 5CrAlZr ODS steel at 700°C are 234 MPa and 58%, respectively. The strengthening mechanisms underlying were also discussed.