X.B.Liu
,
L.Z.Ma
,
K.M.Chang
,
E.Barbero
金属学报(英文版)
Time-dependent Fatigue Crack Propagation (FCP) behaviors of five Ni-base superalloys were investigated at various temperatures under fatigue with various holding times and sustained loading conditions. The new concept of damage zone is defined and employed to evaluate the alloys' resistance to hold-time FCP. A special testing procedure is designed to get the maximum damage zone of the alloys. Udimet 720 and Waspaloy show shorter damage zones than alloys 706 and 718. The fractographieal analyses show that the fracture surfaces of the specimens under hold-time fatigue conditions are mixtures with intergranular and transgranular modes. As the extension of holding time per cycle, the portion of intergranular fracture increases, The effects of loading stress intensity, temperature, holding time, alloy chemisty, and alloy microstructure on damage zone and the crack growth behaviors are studied. Hold-time usually increases the alloy's FCP rate, but there are few exemptions. For instance, the steady, state hold-time FCP rate of Waspaloy at 760℃ is lower than that without hold-time. The beneficial effect of hold-time was attributed to the creep caused stress relaxation during the hold-time.
关键词:
Ni-base superalloys
,
null
,
null
LIU Yuesheng ZHAO Xianguo LIU Zhizhong XIE Xishan Beijing Institute of Aeronautical Materials
,
100095
,
China. University of Science and Technology Beijing
,
100083
,
China.To whom correspondence should be addressed.
材料科学技术（英）
On the basis of an investigation on σ phase in Ni-base cast superalloy K24 and the results about σ phase in other Ni-base superalloys,an embrittl- ing mechanism and a softening mechanism,by which platelike σ phase weakens the Ni-base superalloys,have been proposed.It is considered that the platelike morphology and the habit precipi- tation along{111}of σ phase are necessary condi- tions for both mechanisms.The embrittling mecha- nism is dominant at room temperature and high strain rate,and the softening mechanism is domi- nant at high temperature and low strain rate.Ac- cording to the idea of the softening mechanism and the analyses of σ phase and alloy compositions,it is considered that Nb,Mo and W in the alloys may be resistant to the detrimental effect of σ phase on the stress-rupture properties of the alloys.
关键词:
Ni-base superalloys
,
null
,
null
于晶晶
,
王清
,
李晓娜
,
石尧
,
董闯
,
冀春俊
,
徐香明
材料热处理学报
应用“团簇加连接原子”结构模型对镍基高温合金成分进行了解析,指出了这些合金均源自基础团簇式[Cr-Ni12]Cr3,其中[Cr-Ni12]为在FCC结构中以Cr为心的立方八面体团簇,搭配以3个Cr作为连接原子.根据合金化组元与基体Ni的混合焓大小确定其在团簇式中的位置,最终形成多元合金化后的团簇式[(Al/Ti/Nb)-(Ni/Fe/Co)12](Cr/Al)3.采用铜模吸铸快冷技术制备φ10 mm的合金棒,并对其在1373 K保温2h后空冷.结果表明团簇式中含有一个Al时会有细小的γ'相析出,含有两个Al时[Al-(Ni10Fe2)](Cr2Al)合金中γ'相球形析出,粒子尺寸为30 ～ 60 nm；硬度测试表明前者强化效果不明显,后者由于γ'粒子长大使得合金硬度提高.当Al/Ti/Nb等比例占据团簇心部时,[(Al1/3 Ti1/3 Nb1/3)-(Ni10 Fe2)]Cr3合金的硬度最高,为2.86 GPa.
关键词:
镍基高温合金
,
γ '析出相
,
"团簇加连接原子"模型
