Optimization of microstructure and tensile properties for a 13Cr-1W ODS steel prepared by mechanical alloying and spark plasma sintering using pre-alloyed powder

An oxide-dispersion-strengthened (ODS) 13Cr-1W steel has been fabricated through mechanical alloying (MA) and spark plasma sintering (SPS) using pre-alloyed Fe-Cr-W-Y powder and TiO2 powder. Sufficient MA effects, indicated by homogeneous distribution of alloying elements and high level of lattice strain inside the powder, have been obtained within 20 h of high-energy ball-milling. Grain refinement of the bulk materials is successfully achieved by optimizing the sintering temperature and pressure during SPS. A fine-grained ODS steel with average grain size of 626.75 nm is prepared when sintered at 950 degrees C/80 MPa. Ultrafine oxide dispersoids, identified as Y2O3, Y2TiO5 and Y2Ti2O7, are observed homogeneously distributed in the steel matrix after annealing. They have a number density of 4.5 x 1022 m 3 and an average size of 11.15 nm. Tensile tests from room temperature to 700 degrees C are conducted to this ODS steel. It exhibits an ultimate tensile strength and a yield strength of 1559.60 MPa and 1352.82 MPa at room temperature, respectively. Due to a good combination of dislocation strength-ening, grain boundary strengthening and precipitation strengthening, this alloy wins superior tensile properties over most of the commercial ODS steels and those reported in some previous studies.