FGH95合金长期时效过程中二次γ′相的“反粗化”分裂行为

Reverse Coarsening Splitting Behavior of the Secondary γ′ in Superalloy FGH 95 during Long-Term Aging

摘要:

利用场发射扫描电镜研究了FGH95粉末冶金高温合金在750 ℃/5000 h时效过程中二次γ′相的尺寸、分布和形貌变化，为其在新型航空发动机中的应用提供理论依据。结果表明，随着时效时间增加，二次γ′相形态不稳定，其尺寸变化不符合体扩散控制的LSW规律。二次γ′相在0~500 h发生“反粗化”的分裂，由碟状分裂为块状。在500~1000 h阶段分裂的细小γ′相发生粗化，在1000 h粗化到一定程度后又开始分裂，2000 h后随着时效时间延长又逐渐粗化，椭球状二次γ′相逐渐增多。研究证明，γ′相粒子之间的弹性交互作用是导致其形态变化的主要原因，它属于降低界面能与弹性交互作用能总量的形貌转变机制。

Abstract:

The size, the distribution and the shape of secondary γ′ in powder metallurgy superalloy FGH95 were researched by field emission scanning electron microscopy, the alloy was long-term aged at 750 °C for 5000 h, in order to provide a theoretical basis for its application in newly aero-engines. The results show that with prolonging of the aging time, the morphological character of secondary γ' is unstable, and its size does not follow the law of LSW theory. During 0~500 h the splitting of reverse coarsening occurs in the second γ', resulting in splitting of a single butterfly precipitate into a group of eight cuboids. In 500~1000 h, the split γ′ coarsens to a certain extent and then start to split again after 1000 h. With prolonging of the aging time, they gradually grow after 2000 h, ellipsoidal secondary γ' phase become more and more. It is proved that the shape evolution strongly depends on the elastic interaction between γ' precipitates. Shape changes in order to minimize the sum of interfacial and elastic interaction energies.