第二代单晶高温合金的低周疲劳行为

Low cycle fatigue behavior of a second generation single crystal superalloy DD6 at high temperature

研究了含0.34%Hf DD6单晶高温合金在760℃下的低周疲劳行为,对其疲劳裂纹的萌生与扩展进行了分析。结果表明,含0.34%Hf DD6合金比含0.10%Hf的疲劳寿命稍有降低;其损伤以弹性损伤为主。疲劳裂纹萌生于试样表面、亚表面或试样内部后,先沿垂直应力轴方向扩展,后沿{111}面扩展。其断裂机制为类解理断裂。断口上有典型的疲劳条带。断裂组织分析表明,位错主要在基体通道中扩展,变形后期切过γ'相,形成滑移带。

Low cycle fatigue（LCF） behavior of single crystal superalloy DD6 with 0.34%Hf at 760 ℃ was investigated.The results show that the LCF life of the DD6 alloy with 0.34%Hf is a little shorter than that with 0.10%Hf.The LCF fatigue damage is dominantly ascribed to elastic damage.SEM observations show that the fatigue cracks initiate at the surface and/or near the surface or interior of the specimens.Once initiated,the crack propagates perpendicularly to the loading direction at first and then along {111} plane.The specimens exhibit qusi-cleavage fracture.Typical fatigue striations form in sub-critical fatigue crack propagation region of the fracture surface.TEM observations show that dislocations mainly appear in the matrix,passing through particles and forming slip bands at last stage.