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研究了200、300、400℃温度下N18(NZ2)合金的循环变形行为,同时研究了室温和400℃低周疲劳行为。结果表明:N18(NZ2)合金低周疲劳寿命Nf随着塑性应变范围?εp的增加而降低,并遵循Coffin-Manson关系:Nfβ?εp=C;N18(NZ2)合金在400℃高温下,其循环滞后回线出现锯齿状波形,即出现Portevin-LeChatelier效应。且在200、300、400℃下,合金表现出与常温下不同的循环特性,呈现出一致循环硬化的现象;在高温下,N18(NZ2)合金疲劳断口局部出现韧窝型断裂,并出现细小的二次裂纹。大量二次裂纹的存在是400℃疲劳断口的主要特征。
The cyclic deformation behavior of N18 (NZ2) alloy at temperatures of 200, 300 and 400 ℃ was investigated. The low cycle fatigue behavior at room temperature and 400 ℃ was also studied. The results show that the low cycle fatigue life Nf of N18 (NZ2) alloy decreases with the increase of the plastic strain range εεp and follows the relationship of Coffin-Manson: Nfβ εp = C; N18 (NZ2) Circular sawtooth loop lag serrated waveform, that is, the Portevin-LeChatelier effect. At 200,300,400 ℃, the alloys exhibited different cycle characteristics at room temperature and exhibited a uniform cyclic hardening phenomenon. At high temperature, the fatigue fracture of N18 (NZ2) alloy was locally dimple-fractured and appeared small Secondary crack. The existence of a large number of secondary cracks is the main feature of fatigue fracture at 400 ℃.