Development of oxide dispersion strengthened ferritic steel with enhanced strength–ductility combination through dispersion strengthening and back stress hardening

Oxide dispersion strengthened (ODS) ferritic steel is a potential structural material for fast neutron reactor and fusion reactor application. In this study, a new Fe–13Cr–2W-0.4Ti-0.6Zr/0.35Y2O3 ODS ferritic steel was designed and fabricated through hot isostatic pressing. Results show that the ODS ferritic steel consists of highly dispersive nano-oxide particles, identified as Y2(Ti0.4Zr0.6)2O7 and Y4Zr3O12, with average particle size of 5.34 nm and particle distribution density of 4.2 × 1023 m−3. In addition, heterogeneous coarse/ultrafine grains (CGs/UFGs) structure is also achieved in the matrix. The Fe–13Cr–2W-0.4Ti-0.6Zr/0.35Y2O3 ODS ferritic steel exhibits superior mechanical properties at both room temperature (σb = 1208 MPa, δ = 14%) and high temperature (σb, 700°C = 382 MPa, δ700°C = 32%). The high strength is mainly due to the synergistic effect of particle dispersion strengthening and back stress strengthening, while the good ductility can be attributed to the excellent deformation ability of the coarse grains and the back stress hardening effect induced by the heterogeneous CGs/UFGs structure.