Fatigue crack propagation behavior of IN718 superalloy aged with or without stress was investigated. The alloy aged with stress exhibited a higher fatigue crack growth rate and a lower fatigue threshold compared to that without stress. Both the restricted dislocation planar slip and the decreased difference in orientation of the activated slip system between adjacent grains were promoted by coarse γ″ phases, which increased the local plastic deformation and reduced the crack deflection. The accelerated coarse γ″ phase caused by applied stress was the key factor for the degradation of fatigue crack propagation resistance of the alloy aged with stress.

中文翻译：

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IN718高温合金时效温度/应力耦合场疲劳裂纹扩展行为

研究了 IN718 高温合金有无应力时效时的疲劳裂纹扩展行为。与无应力时效合金相比，有应力时效合金表现出更高的疲劳裂纹扩展速率和更低的疲劳阈值。粗大的γ″相促进了受限位错平面滑移和相邻晶粒之间活化滑移系统取向差异的减小，从而增加了局部塑性变形并减少了裂纹偏转。外加应力引起的加速粗γ″相是应力时效合金抗疲劳裂纹扩展性能下降的关键因素。