Abstract The microstructure evolution and mechanical property degradation are investigated for a nickel-based single crystal superalloy during 1000~1100°C thermal exposure for up to 1000 h. Microstructure analyses are aimed at the coarsening of γ′ precipitates and the formation of rafted structure. The morphology of γ/γ′ phase is described by the coarsening parameter λ′ and the degree of rafting ξ depending on aging time and temperature. The non-monotonic change in the volume fraction of γ′ phase, caused by aging, is also considered. Multi-directional observations reveal that the aged superalloy displays cubic anisotropy with layered rafting structure blocks. The compression experiment results show that elastic modulus is independent of the aging process, but the yield strength degraded exponentially and drops close to 30% after 500 h aging. Relationships among microstructure evolution, aging time/temperature, and macroscopic mechanical property are discussed and proposed. It is confirmed that the material degradation is not only related to the morphology of γ/γ′ phase, but also depends on the precipitation of harmful phases, such as the TCP phase from thermal exposure. The material strength of the aged single crystal superalloy is expressed as a function of microstructure characteristics.

中文翻译：

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具有长期时效效应的镍基单晶高温合金微观结构演变与力学行为的相关性

摘要 研究了镍基单晶高温合金在 1000~1100°C 热暴露达 1000 h 期间的微观结构演变和力学性能退化。显微组织分析的目标是γ'析出物的粗化和筏状结构的形成。γ/γ' 相的形态由粗化参数 λ' 和漂流度 ξ 描述，取决于时效时间和温度。还考虑了由时效引起的 γ' 相体积分数的非单调变化。多方向观察表明，时效高温合金显示出具有层状漂流结构块的立方各向异性。压缩实验结果表明，弹性模量与老化过程无关，但屈服强度呈指数下降，老化 500 小时后下降近 30%。讨论并提出了微观结构演变、时效时间/温度和宏观力学性能之间的关系。经证实，材料降解不仅与γ/γ'相的形貌有关，还取决于有害相的析出，例如热暴露产生的TCP相。时效单晶高温合金的材料强度表示为微观结构特征的函数。