(中国科学院 金属研究所 高温合金部， 沈阳 110016)
摘 要: 研究了K44合金900 ℃低周疲劳性能和断裂行为。 研究结果表明， 该合金在循环形变过程中， 首先表现出起始循环硬化或软化， 随后循环稳定及最终失稳断裂三阶段。 高应变幅下位错切割γ′相形成层错， 降低变形阻力， 合金表现出循环软化行为； 低应变幅下位错在γ′相前塞积造成位错可动性降低， 合金表现出循环硬化行为。 疲劳裂纹主要萌生于试样表面或近表面缺陷处， 以穿晶方式扩展； 合金基体中块状碳化物对裂纹扩展起阻滞作用。
关键字: 抗热腐蚀高温合金； K44； 低周疲劳； 循环应力响应； 疲劳裂纹
（ Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China）
Abstract: Low cycle fatigue(LCF) property and fracture behavior for alloy K44 at 900 ℃ were investigated. The results show that the LCF property of alloy K44 under various strain amplitudes can be characterized by three stages: the stage of initial cyclic hardening or softening behavior, the stage of continuous cyclic stability, and then the stage of rapid fracture. TEM observations show that, at high strain amplitudes the softening behavior can be attributed to the formation of stacking faults from dislocation cutting in γ′ particles, while at low strain amplitues the hardening behavior results from the decrease of mobility of dislocations due to the piling up of dislocations before γ′ particles. SEM observations show that the fatigue cracks initiate dominantly on the surface and/or at cast defects near the surface, and propagate in transgranular manner. The existence of block carbides in the matrix can retard effectively crack propagation.
Key words: corrosion-resistant superalloy; K44; low cycle fatigue; cyclic stress response; fatigue crack
