Low cycle fatigue of as-HIP and HIP+forged rené 95
Low cycle fatigue of as-HIP and HIP+forged rené 95
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as-HIP 和 HIP+forged rené 95 的低周疲劳
DOI：
10.1007/bf02812013
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发表时间：
1979
期刊：
影响因子：
--
通讯作者：
S. Antolovich
中科院分区：
文献类型：
--
作者：
S. Bashir;P. Taupin;S. Antolovich
在热等静压和热等静压+锻造条件下，使用粉末产品（-60目）在649°C下研究了镍基高温合金René 95的连续循环和保持时间低周疲劳性能。结果表明，裂纹是由孔隙，陶瓷颗粒和经典的第一阶段的机制，两种材料和两个周期字符。对于连续循环的热等静压材料，变形仅限于在低应变下定义良好的带，并随着应变水平的增加而变得均匀。断裂总能量在低应变状态下突然增加，这也反映在Coffin-Manson图的断裂上。在所有情况下，裂纹都是在孔隙处产生的。保持时间试样表现出极高的位错密度和表面连接的初始化，但没有显着的寿命降低。HIP +锻造材料的观察结果基本相似，除了变形倾向于局限于明确定义的滑移带，即使在高应变下，在一定程度上甚至对于保持时间测试。这种行为归因于γ′更小、更共格且更容易被强配对的位错剪切。在裂纹长度和塑性应变的独特组合下，裂纹扩展从穿晶变为晶间（也观察到了热等静压材料）有明显的趋势。过渡发生在较短的裂纹长度的HIP +锻造材料，除了当裂纹萌生是次表面。在这种情况下，过渡被延迟，寿命大大提高，这表明环境在确定疲劳寿命方面起着重要作用。
The continuous cycling and hold time low cycle fatigue properties of the Ni base superalloy René 95 were studied at 649°C using powder products (−60 mesh) in the as-HIP and HIP + forged conditions. It was shown that cracks were initiated by pores, by ceramic particles and by a classical stage I mechanism for both materials and for both cycle characters. For the continuously cycled as-HIP material, deformation was restricted to well defined bands at low strains and became homogeneous as the strain level increased. The total energy to fracture increased abruptly in the low strain regime and this was also reflected by a break in the Coffin-Manson plot. In all cases cracks initiated at pores. The hold time specimens exhibited an extremely high dislocation density and surface connected initiation yet without a significant life reduction. The observations were essentially similar for the HIP + forged material except that deformation tended to be confined to well defined slip bands even at high strains and to some extent even for the hold time tests. This behavior was attributed to the fact that theγ′ were smaller, more coherent and more readily sheared by dislocations which were strongly paired. There was a marked tendency for crack propagation to change from transgranular to intergranular (also observed for the as-HIP material) at a unique combination of crack length and plastic strain. The transition occurred at shorter crack lengths for the HIP + forged material except when crack initiation was subsurface. In this case the transition was delayed and the life was greatly enhanced, indicating that the environment plays a major role in determining the fatigue life.