中文摘要：

研究了粉末冶金镍基高温合金FGH97在650℃,30—980 MPa,1 Hz实验条件下的低周疲劳断口的宏观及微观特征,裂纹源的类型及其形貌特征,以及裂纹源的位置、缺陷类型、形状和尺寸对低周疲劳寿命的影响.结果表明,在本次实验条件下该合金的低周疲劳寿命均超过了5000 cyc;统计得出,低周疲劳断口裂纹源在表面的试样占23%,在亚表面的占47%,在试样内部的占30%;裂纹源分平台、粉末颗粒、夹杂物3种类型,其中平台类型约占5%,粉末颗粒间断裂占15%,夹杂物占80%.由统计分析和计算得出,不同类型裂纹源对疲劳寿命的影响程度不同：夹杂物最严重,其次为异常粉末颗粒,再次为局部塑性变形.

英文摘要：

Powder metallurgy（P/M） nickel-based superalloy FGH97 has been researched in recent 10 years in China which is particularly suitable for producing aircraft engine disks and shafts etc..In the range of operating temperature,the resistance to low cycle fatigue（LCF） of P/M nickelbased superalloy is one of the most important performances.In this paper the fracture features of LCF on P/M nickel-based superalloy FGH97 were investigated.The study focused on macroscopic and microscopic features of LCF fractures under 650℃,980-30 MPa,1 Hz test conditions by optical microscope and SEM.The types and morphologies of failure origins were observed.The effects of failure origin location and type,shape and size of defects located in fracture on LCF life were discussed.The results show that LCF life of all the specimens of FGH97 is over 5000 cyc under above test conditions. Statistically,23%of LCF failure origins are on sample surface,47%near surface and 30%in interior of samples.There are statistically three types of the LCF failure origins in this alloy：5%of grain facet,15%of powder particle and 80%of inclusion.Based on the statistical analysis and theoretical calculation of the influences of three types of LCF failure origins on LCF life,it can be concluded that the LCF life can be more severely affected by the inclusion than by the abnormal powder particle and partial plastic deformation.