粉末镍基U720Li高温合金长期时效下的组织与性能稳定性

Microstructure and Property Stability of Powder Metallurgy Nickel-based U720Li Superalloy During Long-Term Aging

摘要:

研究了经粉末冶金的镍基U720Li高温合金在680、700和730 ℃长期时效（3000 h）下的组织演变及力学性能变化，表征了γ′相在长期时效过程中的形貌与尺寸变化。结果表明，γ′相粗化行为由扩散过程控制。在680和700 ℃下的长期时效过程中，U720Li高温合金的抗拉伸和蠕变性能保持稳定；但在730 ℃/500 h长期时效后，合金屈服强度逐渐降低，塑性增加。在730 ℃长期时效过程中，U720Li高温合金的疲劳和蠕变性能急剧下降，这与γ′相的形貌演变有关。

Abstract:

The microstructure evolution and variation of mechanical properties of nickel-based U720Li superalloy were investigated during long-term aging (3000 h) at 680, 700, and 730 °C. The changes in size and morphology of γ′ phase were determined. Results show that the coarsening behavior of γ′ phase is controlled by the diffusion process. The tensile and creep properties of U720Li superalloy remain stable during the long-term aging at 680 and 700 °C. However, the yield strength gradually decreases and the ductility increases after long-term aging at 730 °C for 500 h. The fatigue and creep properties of U720Li superalloy decreases sharply after long-term aging at 730 °C, which is mainly related to the morphology evolution of γ′ phase.