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(EDS)仪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合金在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。
A series of axial force controlled fatigue tests at 1070℃ were 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.Fracture morphology and microstructure of these samples were characterized by scanning electron microscopy (SEM)and energy dispersive spectroscopy (EDS)in order to analyze the fracture micro-mechanism at different stress ratios.The results indicate that the high cycle fatigue life of DD6 alloy with different stress ratios 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 in stress ratio.The fatigue life of DD6 alloy increases with the increase in 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 life of the alloy.Analysis on fracture surfaces of DD6 alloy at 1070℃ demonstrates that a quasi-cleavage mode is observed under the condition of low stress ratio,while a dimple mode is found at high stress ratio.The fatigue fracture mode under medium stress ratio has the mixing characteristics of the above mentioned modes.High temperature oxidation under low stress ratio is helpful to the initiation and propagation of cracks.
作者
谢洪吉
李嘉荣
韩梅
Xie Hongji;Li Jiarong;Han Mei(Science and Technology on Advanced High Temperature Structural Materials Laboratory,Beijing Institute of Aeronautical Materials,Beijing 100095,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2018年第11期3381-3386,共6页
Rare Metal Materials and Engineering
关键词
单晶高温合金
应力比
高周疲劳行为:断裂模式
single crystal superalloy
stress ratio
high cycle fatigue behavior
fracture model
