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研究含晶界强化元素碳、硼和铪的第二代镍基单晶高温合金DD5的组织演化和稳定性。利用光学显微镜、扫描电镜、电子探针、能量分散光谱和萃取试验研究DD5合金的铸态、热处理态和热暴露后的微观组织和成分。在铸态条件下，γ相为初生凝固相，枝晶间存在3种偏析相，其形貌取决于元素偏析程度。热处理后，枝晶杆内γ′相细小且立方化程度高，尺寸约为0.5μm，质量分数为61.685%，枝晶间存在不规则γ′相和MC/M23C6碳化物。经980°C、1000 h热暴露后，未发现TCP相析出，表明DD5合金在980°C具有较好的组织稳定性。

The microstructual evolution and stability of a second generation single crystal (SC) nickel-based superalloy DD5 with minor grain boundary (GB) strengthening elements (C, B and Hf) were studied as a function of as-cast, heat treatment and thermal exposure. The microstructure and composition of the alloy were investigated by optical microscopy, scanning electron microanalysis (SEM), electron probe microanalysis (EPMA), energy dispersive spectrometry (EDS) and extraction analysis. In the as-cast condition, the microstructure observations and composition analysis showed thatγphase was the primary solidification phase and there were three microsegregations in the metal matrix. The morphology of these microsegregations depended on element segregations. After heat treatment, the dendrite cores contained fine and cuboidal-shapedγ′particles with an average edge length of about 0.5μm, while interdendritic regions contained irregularly-shapedγ′particles and MC/M23C6 carbides. The mass fraction ofγ′phases was 61.685%. After exposure at 980 °C for 1000 h, no TCP phase was observed in both dendritic and interdendritic regions, indicating a good microstructual stability of the DD5 alloy at 980 °C.