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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 microstructure evolution and stability of the second generation nickel base single crystal superalloy DD5 with grain boundary strengthening elements of carbon, boron and hafnium were investigated. The microstructure and composition of DD5 alloy after as-cast, heat-treated and thermal exposure were studied by optical microscope, scanning electron microscopy, electron probe, energy dispersive spectroscopy and extraction experiments. Under the as-cast condition, the γ phase is the primary solidified phase, and there are three segregation phases between the dendrites. The morphology depends on the degree of element segregation. After heat treatment, the γ ’phase in the dendrite rod is small and has a high degree of cubitization with a size of about 0.5 μm and a mass fraction of 61.685%. There are irregular γ’ phases and MC / M23C6 carbides between the dendrites. After thermal exposure at 980 ° C for 1000 h, no TCP phase precipitation was observed, indicating that the DD5 alloy has good tissue stability at 980 ° C.