Characterization of Microstructure and Stability of Precipitation in SIMP Steel Irradiated with Energetic Fe Ions

A type of home-made reduced activation martensitic steel, high silicon (SIMP) steel, is homogeneously irradiated with energetic Fe ions to the doses of 0.1, 0.25 and 1 displacement per atom (dpa), respectively, at 300^\circ\!C and 1 dpa, at 400^\circ\!C. Microstructural changes are investigated in detail by transmission electron microscopy with cross-section technique. Interstitial defects and defect clusters induced by Fe-ion irradiation are observed in all the specimens under different conditions. It is found that with increasing irradiation temperature, size of defect clusters increases while the density drops quickly. The results of element chemical mapping from the STEM images indicate that the Si element enrichment and Ta element depletion occur inside the precipitates in the matrix of SIMP steel irradiated to a dose of 1 dpa at 300^\circ\!C. Correlations between the microstructure and irradiation conditions are briefly discussed.