(中國科學院 金屬研究所 高溫合金部， 沈陽 110016)
摘 要: 研究了K44合金900 ℃低周疲勞性能和斷裂行為。 研究結果表明， 該合金在循環(huán)形變過程中， 首先表現(xiàn)出起始循環(huán)硬化或軟化， 隨后循環(huán)穩(wěn)定及最終失穩(wěn)斷裂三階段。 高應變幅下位錯切割γ′相形成層錯， 降低變形阻力， 合金表現(xiàn)出循環(huán)軟化行為； 低應變幅下位錯在γ′相前塞積造成位錯可動性降低， 合金表現(xiàn)出循環(huán)硬化行為。 疲勞裂紋主要萌生于試樣表面或近表面缺陷處， 以穿晶方式擴展； 合金基體中塊狀碳化物對裂紋擴展起阻滯作用。
關鍵字: 抗熱腐蝕高溫合金； K44； 低周疲勞； 循環(huán)應力響應； 疲勞裂紋
（ 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
