Ferritic Martensitic (F/M) steel HT9 specimens were irradiated in the Advanced Test Reactor up to 4.16 dpa in three temperature ranges (roughly from 300 to 600 °C). The post-irradiation microstructure, including dislocation structure, precipitation and radiation-induced segregation (RIS) was characterized using analytical scanning / transmission electron microscopy (S/TEM), and atom probe tomography (APT). Irradiation hardening was measured using nanoindentation. The results reveal a distinctive pattern of dislocation and precipitate evolution at high temperature, around 600 °C, where various defects and precipitates formed in the low dose regime followed by a recovering process with increasing dose. Dislocation loops formed in all temperature ranges, and the growth of dislocation loops is unconstrained above certain critical temperature, contributing to the increasing dislocation density even prior to doses of 0.5 dpa at 600 °C. Ni/Mn/Si clusters were identified in all temperature ranges and the compositions of these clusters converged to G phase stoichiometrically. Significant coarsening of G phase particles was observed at 600 °C, accompanied by the formation of G phase on grain boundaries. α’ precipitates were only found in the medium and low temperature ranges (below 500 °C). The number density and volume fraction were higher in the low temperature specimens, while larger particles were observed in the medium temperature range. RIS of Cr, Ni, Mn, Si, P was identified at dislocation lines, grain boundaries and phase boundaries, and the temperature dependence is consistent with previous studies. The RIS of Cr to the existing VN particles was confirmed by APT and may accelerate the transition of VN to Cr-rich nitrides. The irradiation hardening contribution from dislocation loops, dislocation lines, G phase and α’ phase was parsed based on a linear dispersed barrier hardening model. The results suggest that most irradiation hardening at high temperature is due to increasing dislocation density with dose.

铁素体马氏体 (F/M) 钢 HT9 试样在高级测试反应器中在三个温度范围内（大约从 300 到 600 °C）进行高达 4.16 dpa 的辐照。使用分析扫描/透射电子显微镜 (S/TEM) 和原子探针断层扫描 (APT) 表征辐射后的微观结构，包括位错结构、沉淀和辐射诱导偏析 (RIS)。使用纳米压痕测量辐照硬化。结果揭示了在 600°C 左右的高温下位错和沉淀物演化的独特模式，其中在低剂量方案中形成了各种缺陷和沉淀物，然后随着剂量的增加而恢复过程。在所有温度范围内都会形成位错环，并且在一定临界温度以上位错环的生长不受约束，甚至在 600 °C 下 0.5 dpa 的剂量之前也有助于增加位错密度。Ni/Mn/Si 团簇在所有温度范围内都被识别出来，这些团簇的组成趋于G相化学计量。在 600 °C 时观察到G相颗粒显着粗化，同时在晶界形成G相。α' 沉淀物仅在中低温范围内（低于 500 °C）发现。低温试样的数密度和体积分数较高，而在中等温度范围内观察到较大的颗粒。在位错线、晶界和相界处识别出 Cr、Ni、Mn、Si、P 的 RIS，其温度依赖性与先前的研究一致。APT 证实了 Cr 对现有 VN 颗粒的 RIS，并可能加速 VN 向富铬氮化物的转变。位错环、位错线、G相和α的辐照硬化贡献' 相基于线性分散屏障硬化模型进行解析。结果表明，大多数高温辐照硬化是由于位错密度随剂量增加而增加的。