硅对低膨胀高温合金组织和持久性能的影响

Effects of Silicon on Microstructure and Stress Rupture Properties of Low Thermal Expansion Superalloy

研究了硅对Ｆｅ－Ｎｉ－Ｃｏ基高强度低膨胀高温合金组织和持久性能的影响。探讨了硅提高合金持久性能、消除持久缺口敏感性的机理。结果表明，硅细化晶粒、提高持久塑性。硅促进ε、Ｌａｖｅｓ和Ｇ相的析出，使ε相由六方结构转变为正交结构，使晶界ε相由连续的薄膜分布转变成分散的块状甚至球状。硅减小γ′相点阵常数及与基体的错配度，提高了γ′的稳定性。

The effects of silicon on microstructure and stressrupture properties of a FeNiCo base superalloy with high strength and low thermal expansion coefficient have been investigated. The mechanisms of the beneficial role of silicon in improving stressrupture life and eliminating notchbar sensitivity of the alloy were also disclosed. It was found that silicon can refine grain size of the alloy. Silicon can also accelerate the precipitation of ε, Laves and G phases. With the increase of silicon content in the alloy, the crystal structure of ε phase transforms from hexagonal system to orthogonal one. At the same time, the continuous filmlike ε phase at the grain boundaries alters to discontinuous block or sphere morphology. Silicon can reduce crystal lattice constant of γ′ phase and decrease the mismatch between γ′ and matrix. Thus these can improve stability of the γ′ phase.