FGH96镍基高温合金的高温低周疲劳断裂机理研究

Low Cycle Fatigue Fracture Mechanism at Elevated Temperature for FGH96 Nickel-base Superalloy

研究了FGH96镍基高温合金在550,720℃条件下应变控制的高温低周疲劳断裂机理。结合断口宏微观观察和位错组织结构观察,探讨了FGH96合金疲劳行为的微观机理,并建立了扩展区面积和疲劳寿命的定量关系,结果表明:FGH96合金的断裂特征以穿晶解理为主;合金在较高温度下具有较低的疲劳寿命是与氧化损伤和合金的塑性变形密切相关;应变幅较小时(<0.6%左右),温度对合金的疲劳寿命起主导作用,氧化损伤效应明显;位错密度在较高的应变幅下比在较低的应变幅下高得多,较高应变幅下,位错发生了交滑移甚至是攀移运动;合金的疲劳断口扩展区面积与疲劳寿命存在线性对数关系。

Low cycle fatigue tests were conducted on FGH96 nickel-base superalloy with total strain amplitude from ±0.4% to ±0.8% at 550℃ and 720℃. The fatigue behavior and micromechanism of the alloy were studied through scanning electron microscopy（SEM） and transmission electron microscopy（TEM） ,and the correlations between the areas of fatigue propagation region and the cycles of fatigue were established. The results show that FGH96 fatigue fracture characteristic is brittle intergranular,the alloy possesses lower fatigue lifetime at higher temperature that is relevant to oxidation damage and cyclic deformation, the tests temperature plays an important role to fatigue lifetime and oxidation damage effect is evident when the strain amplitude is lower（〈0.6M）. The dislocation density is much higher at higher strain amplitude and the dislocation occurrs cross sliding and climbing. The relationship between logarithmic areas of fatigue propagation region and logarithmic fatigue lifetime is linear.