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应力比对单晶高温合金高周疲劳行为的影响
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北京航空材料研究院先进高温结构重点实验室

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TG132.3

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Effect of Stress Ratio on High Cycle Fatigue Behavior ofa Single Crystal Superalloy
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Science and Technology on Advanced High Temperature Structural Materials Laboratory,Beijing Institute of Aeronautical Materials

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    摘要:

    为了研究应力比对DD6单晶高温合金高周疲劳行为的影响,在轴向疲劳试验机上分别测试了DD6合金1070℃条件下应力比为-1、-0.33、0.1、0.5、0.8的疲劳性能,采用扫描电镜(SEM)和能谱仪(EDS)观察分析了不同应力比合金的断口形貌和显微组织。结果表明:DD6合金不同应力比条件下的疲劳寿命均随应力幅值和平均应力的增加而降低;当应力幅值恒定时,DD6合金疲劳寿命随着应力比的增大而降低;当平均应力恒定时,应力比R<0.5条件下的疲劳寿命随着应力比的增大而增加,同时,当平均应力增大到一定程度时,应力比对合金的疲劳寿命无明显影响。DD6合金低应力比条件下的疲劳断裂模式为类解理断裂,该条件下高温氧化有助于疲劳裂纹的萌生和扩展;高应力比条件下的疲劳断裂模式为韧窝断裂;中等应力比条件下疲劳断裂模式具有类解理断裂和韧窝断裂同时存在的特征。

    Abstract:

    A series of axial force controlled fatigue tests at 1070℃ had been performed to elucidate the influence of stress ratio (-1/-0.33/0.1/0.5/0.8) on high cycle fatigue behavior of DD6 single crystal superalloy. In order to analyze the fracture micro-mechanism under different stress ratio, fracture morphology and microstructure of these samples were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Experimental results indicate that the high cycle fatigue life of DD6 alloy with different stress ratio decreases with the increase of stress amplitude and mean stress. When the stress amplitude is constant, the fatigue life of DD6 alloy decreases with the increase stress ratio. The fatigue life of DD6 alloy increases with the increase stress ratio when the mean stress is constant and the stress ratio is less than 0.5. However, when the mean stress increases to a certain extent, the stress ratio has no significant effect on the fatigue of the alloy. Analysis on fracture surfaces of DD6 alloy at 1070℃ demonstrates that that quasi-cleavage mode is observed under the condition of low stress ratio, but is dimple mode at high stress ratio. The fatigue fracture mode under medium stress ratio has the mixing characteristics of the above mentioned mode. High temperature oxidation under low stress ratio is helpful to the initiation and propagate of cracks.

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谢洪吉,李嘉荣,韩梅.应力比对单晶高温合金高周疲劳行为的影响[J].稀有金属材料与工程,2018,47(11):3381~3386.[Xie Hongji, Li Jiarong, Han Mei. Effect of Stress Ratio on High Cycle Fatigue Behavior ofa Single Crystal Superalloy[J]. Rare Metal Materials and Engineering,2018,47(11):3381~3386.]
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  • 收稿日期:2017-02-21
  • 最后修改日期:2017-04-10
  • 录用日期:2017-04-13
  • 在线发布日期: 2018-12-19
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