Abstract The long-term stress-rupture life of Nimonic 80A with varied Ti/Al ratios was investigated at 650 °C/300 MPa. The stress-rupture life increases from about 6479 to 7734 and 11713 h, and the duplex grain size distribution evolves from bimodal morphology to near-homogeneous morphology with the decreased Ti/Al ratio. Although the stress-rupture life increases significantly, the stable γ′ homogeneously distributes in γ matrix with a coherent orientation relationship with γ on {100}γ′/γ and {110}γ′/γ atomic planes. With the decreased Ti/Al ratio, more precipitation of TiC particles leads to the depletion of C element near grain boundary, which suppresses precipitation of Cr23C6. A large amount of plate-like Cr23C6 carbide which precipitates at grain boundaries can easily lead to the intergranular cracking, but the blocky Cr23C6 carbide which shows an orientation relationship on {111}γ atomic planes with the nearby matrix at the twin boundary does not cause grain boundary cracking. Lower Ti/Al ratio benefits longer stress-rupture life based on the near-homogeneous duplex grain size distribution and none precipitation of plate-like Cr23C6.

中文翻译：

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降低的 Ti/Al 比改变了 Cr23C6 的析出行为并提高了长期应力断裂寿命

摘要 研究了不同 Ti/Al 比的 Nimonic 80A 在 650 °C/300 MPa 下的长期应力断裂寿命。应力断裂寿命从约 6479 小时增加到 7734 小时和 11713 小时，双相晶粒尺寸分布从双峰形貌演变为接近均匀的形貌，Ti/Al 比降低。虽然应力断裂寿命显着增加，但稳定的γ'均匀分布在γ基体中，与γ在{100}γ'/γ和{110}γ'/γ原子平面上具有相干取向关系。随着Ti/Al比的降低，更多的TiC颗粒析出导致晶界附近C元素的耗尽，从而抑制了Cr23C6的析出。大量在晶界析出的片状Cr23C6碳化物容易导致晶间开裂，但块状 Cr23C6 碳化物在 {111}γ 原子平面上与孪晶界附近的基体显示取向关系，不会引起晶界开裂。基于近乎均匀的双相晶粒尺寸分布和无片状 Cr23C6 析出，较低的 Ti/Al 比有利于更长的应力断裂寿命。