Microstructural characterization and low-cycle fatigue behavior of ODS steel prepared by precursor-assisted cast technology

• The microstructural evolution of cast ODS steel during fatigue process was studied at 650℃. • Nano-oxides reduce cyclic softening by hindering dislocation movement. • Precursor-assisted casting efficiently produces high-performance ODS steel. The microstructural evolution and cyclic deformation behavior of oxide dispersion-strengthened (ODS) steel fabricated by precursor-assisted cast technology (PACT) were systematically investigated through multi-scale characterization methods. Low-cycle fatigue tests were performed at 650 °C with total strain amplitudes ranging from ± 0.4 % to ± 1.0 % to investigate the deformation mechanisms and the stability of nano-oxides. The evolution of dislocation structures and nano-oxide distributions was characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) at critical fatigue stages. Regions with a high oxide density exhibit enhanced resistance to cyclic softening, indicating a strong correlation between dislocation structure evolution and nano-oxide distribution. Fractographic examination using scanning electron microscopy (SEM) reveals transgranular crack propagation without failure initiation at inclusions, confirming the microstructural homogeneity achieved through PACT. This comprehensive characterization demonstrates that the PACT produces ODS steels with stable nano-oxide dispersions and improved resistance to cyclic deformation at elevated temperatures.