Microstructure Evolution and Phase Stability of ODS Steel During Spark Plasma Sintering

The effect of spark plasma sintering (SPS) temperature on the structural and phase state and the physicomechanical properties of an ODS steel based on the Fe-Cr-Y2O3 system was investigated. It was established that increasing the SPS temperature is accompanied by a gradual increase in the degree of consolidation and a reduction in residual porosity. At 1400 °C, the densest and most homogeneous microstructure is formed, and the relative density reaches 96.3%. Further increasing the temperature to 1500 °C has little effect on the degree of consolidation, while the main phase composition, α-Fe(Cr), is retained. According to X-ray diffraction analysis, the crystallite size increases with increasing temperature, whereas the lattice microstrain decreases up to 1400 °C and increases at 1500 °C. The microhardness ranges from 489.4 to 588.7 HV1, reaching a maximum value of 588.7 HV1 at 1500 °C. Based on the combined consolidation and microstructural characteristics, 1400 °C was identified as the optimal SPS temperature, providing the highest degree of densification and the most homogeneous structural state of the material. The results demonstrate that, after a high degree of consolidation has been achieved, further increasing the temperature primarily promotes structural evolution without a significant increase in material density.