Effect of spark plasma sintering temperature on microstructure and mechanical properties of 14Cr-ODS ferritic steels

14% Cr oxide dispersion strengthened (ODS) steels were produced. The effects of sintering temperature on the microstructure and mechanical properties were investigated. The microstructures of 14Cr-ODS steels were characterized by using electron backscattered diffraction (EBSD), transmission electron microscopy (TEM) and synchrotron radiation small angle X-ray scattering (SAXS). The results showed that ultrafine grains are formed in the ODS steels sintered at low temperature, and a mixed microstructure of fine grains and coarse grains is observed in the steels sintered at high temperature. With the increasing of sintering temperature from 950 °C to 1025 °C, the average grain sizes increase from 290 nm to 2420 nm. High-density nanoscale Y-rich oxides and some large Cr-rich oxides are observed. The nanoscale Y-rich oxides are dominated in the SPSed ODS steels. The number density of Y-rich oxides decreases but the average size increases with the increasing sintering temperature, and the size and number density of Cr-rich oxides increase with increasing temperature. The tensile strength of the samples sintered at 950 °C is higher than that of the sample sintered at higher temperature.