【摘要】 系统探讨了温度对第四代粉末高温合金FGH4108低周疲劳变形机制的影响。通过在400～850℃温度下开展应变控制低周疲劳（Low-cycle fatigue, LCF）试验，结合扫描电镜（Scanning electron microscopy, SEM）、电子背散射衍射（Electron backscatter diffraction, EBSD）和透射电镜（Transmission electron microscopy, TEM）等表征手段，揭示了温度主导下合金从循环硬化向循环软化主导机制的演化过程。结果表明，600℃及以下FGH4108合金表现出显著的循环硬化趋势，700℃以上则发生软化，尤以850℃最为显著。断裂模式由穿晶逐步过渡至沿晶，变形机制亦由基体内位错累积转向位错剪切γ’相及层错、孪晶协同机制。TEM观察显示，高温下γ’相稳定性下降，局部区域出现明显的层错结构及局域γ’剪切行为。EBSD分析表明，600～850℃范围内晶内局部畸变整体分布稳定，表明温度对位错密度影响相对有限。研究结果有助于深入理解FGH4108合金高温疲劳行为的演化机制，为新一代粉末高温合金的服役性能评估与优化设计提供理论支撑。更多还原

【Abstract】 This study systematically investigates the influence of temperature on the low-cycle fatigue (LCF) deformation mechanisms of the fourth-generation powder metallurgy (PM) superalloy FGH4108. Strain-controlled fatigue tests were conducted at temperatures ranging from 400 ℃ to 850 ℃, in combination with microstructural characterization techniques including scanning electron microscopy(SEM), electron backscatter diffraction(EBSD), and transmission electron microscopy(TEM). The evolution of the fatigue response from cyclic hardening to softening under temperature control was elucidated. The results show that FGH4108 exhibits significant cyclic hardening behavior at temperatures up to 600 ℃, whereas cyclic softening becomes dominant above 700 ℃, with the most pronounced effect observed at 850 ℃. Fracture mode transitions from transgranular to intergranular with increasing temperature, accompanied by a change in deformation mechanism from dislocation accumulation in the matrix to a combined mechanism of γ′ precipitate shearing, stacking fault formation, and twinning. TEM observations revealed that the γ′ phase exhibits reduced thermal stability at elevated temperatures, with localized stacking faults and γ′ shearing features observed. EBSD analysis indicated that the distribution of intragranular local misorientation remains relatively stable between 600 ℃ and 850 ℃, suggesting a limited influence of temperature on overall dislocation density. These findings provide insights into the temperature-dependent fatigue behavior of FGH4108 and offer theoretical guidance for performance evaluation and design optimization of next-generation PM superalloys.更多还原