Ferritic martensitic ODS steels are one of the candidate structural materials for future Gen-IV nuclear fission and fusion reactors. The dependence of fracture toughness on microstructure was investigated by comparing three 9Cr ODS EUROFER steels manufactured through different thermo-mechanical processing routes. Quasi-static fracture toughness testing was performed with sub-sized C(T) specimens and microstructural characterization was carried out using scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. It was found that at lower test temperatures (−100 – 22 °C), the fracture toughness was primarily controlled by crack initiation at sub-micron particles and by production of secondary cracks during fracture. At higher temperatures (above 100 °C), fracture toughness was predominantly controlled by the matrix ductility and the grain boundary strength with a relatively ductile coarse-grained alloy demonstrating higher fracture toughness compared to high-strength fine-grained alloys. These results and discussion show that variations in thermomechanical treatments can produce significant differences in microstructure and fracture toughness behavior of ferritic martensitic ODS steels.

铁素体马氏体ODS钢是未来的第四代核裂变和聚变反应堆的候选结构材料之一。通过比较三种通过不同热机械加工路线生产的9Cr ODS EUROFER钢，研究了断裂韧度对显微组织的依赖性。对亚尺寸C（T）试样进行了准静态断裂韧性测试，并使用扫描电子显微镜，电子反向散射衍射和透射电子显微镜进行了微结构表征。研究发现，在较低的测试温度（−100 – 22°C）下，断裂韧性主要受亚微米颗粒的裂纹萌生和断裂过程中产生第二道裂纹的控制。在较高温度下（高于100°C），断裂韧性主要由基体延性和晶界强度控制，而相对延性的粗粒合金则比高强度细晶粒合金具有更高的断裂韧性。这些结果和讨论表明，热机械处理的变化会在铁素体马氏体ODS钢的显微组织和断裂韧性行为方面产生重大差异。