Abstract: The low cycle fatigue behavior and fatigue crack growth rate(da / dN) of alloy IN718 were studied in detail at the temperatue of 360℃ 550℃ and 650℃ , including the low cycle fatigue Δε / 2-2Nf curves, cyclic stress-strain behavior, Massing effect, the LCF lives expressed by plastic strain energy and crack growth, rates. The effect of hold time on da/dN was olso discussed.The experimental results show that this alloy appears cyclic softening at various temperature and has Massing characteristic at the test temperatuer, The relationship between plastic strain energy and fatigue life of alloy IN718 is the linear relations on double logarithm coordinate. From 360℃ to 550℃, the change of da / dN of allog 718 is slight, but the da / dN at 650℃ is much higher than that at 550℃. The effect of hold time on da / dN is obvious at 650℃, and the da / dN can be calculated by Equation(18) in this paper.

Key words: Low cycle fatigue, stress-strain behavior, fatigue crack growth rates