Strengthening mechanisms of oxide dispersion strengthened steel

An oxide dispersion strengthened (ODS) ferritic steel with the nominal composition of Fe-12.5Cr-2.5W-0.4Ti-0.02V-0.4Y₂0₃ (designated 12Cr-ODS,% by mass) was produced by powder metallurgy. Its microstructure and mechanical properties were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and mechanical properties testing. Quantitative calculations were performed to find out the contribution of different strengthening mechanisms to the yield strength of the steel. SEM and TEM observations show that the steel exhibits equiaxed ferritic grains, its average size is 1.5 μm, and oxide particles of different sizes appear quite homogeneously distributed in the matrix. Tensile testing results indicate that the steel has superior tensile strength with the high yield strength of 738 MPa at room temperature. Orowan strengthening, work hardening effect of reinforced particles, dislocation strengthening by thermal expansion mismatch, and grain boundary strengthening are the main strengthening mechanisms of the steel. The theoretical yield strength is 750 MPa, which is in good agreement with the experimental data.