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Low cycle fatigue and stress relaxation behaviours of powder metallurgy Ni-based superalloy FGH4098
Materials Science and Engineering: A ( IF 6.4 ) Pub Date : 2021-05-07 , DOI: 10.1016/j.msea.2021.141421
R. Jiang , L.C. Zhang , W.T. Zhang , Y. Zhang , Y. Chen , J.T. Liu , Y.W. Zhang , Y.D. Song

In this study, the effects of microstructure, temperature and dwell time in a loading cycle on low cycle fatigue (LCF) and stress relaxation behaviours of a powder metallurgy Ni-based superalloy (i.e. FGH4098) for aeroengine turbine disc application were studied along with detailed microscopic characterisation of fracture features and deformation substructures. The results indicate that the LCF failure mode of FGH4098 transits from transgranular to intergranular with the increase of temperature and dwell time, and the propensity of intergranular fatigue cracking is higher in fine-grained FGH4098. FGH4098 predominantly shows cyclic hardening behaviour which is mainly related to dislocation interactions. With the increase of temperature and/or dwell time, the cyclic hardening behaviour diminishes to some extent due to the increasing shearing of secondary γ′ precipitates by stacking fault and partial dislocation pairs. Similarly, stress relaxation in FGH4098 is also associated with the shearing of γ′ precipitates and becomes more prominent at high temperature with long dwell period. Micro-twinning may also contribute to stress relaxation at 750 °C.



中文翻译:

粉末冶金镍基高温合金FGH4098的低周疲劳和应力松弛行为

在这项研究中,研究了在加载循环中的微观结构,温度和停留时间对航空发动机涡轮盘应用的粉末冶金镍基高温合金(即FGH4098)的低循环疲劳(LCF)和应力松弛行为的影响。断裂特征和变形子结构的微观表征。结果表明,随着温度和停留时间的增加,FGH4098的LCF破坏模式由晶间转变为晶间,细晶FGH4098的晶间疲劳裂纹倾向更高。FGH4098主要表现出循环硬化行为,这主要与位错相互作用有关。随着温度和/或保压时间的增加,由于堆垛层错和部分位错对对次生γ′沉淀物的剪切作用增加,循环硬化行为在一定程度上减弱了。同样,FGH4098中的应力松弛也与γ'析出物的剪切有关,并且在高温下具有较长的停留时间时应力松弛更为明显。微孪晶也可能有助于在750°C时缓解应力。

更新日期:2021-05-13
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