Crystallographic Fracture Mechanics Study on Creep-Fatigue Small Crack Propagation in Ni-base Superalloyas at High Temperatures

镍基高温合金高温蠕变疲劳小裂纹扩展的晶体断裂力学研究

基本信息

批准号：
04650080
负责人：
OKAZAKI Masakazu
金额：
$ 1.34万
依托单位：
Nagaoka University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

Small fatigue crack growth behavior was investigated in three kinds of Ni-base superalloys at high temperatues ; a single crystal alloy, a directionally-solidified alloy and a pollycrystalline alloy. The effects of temperature and microstructures were also studies base on the muasurement of the crack openig and closing behavior.The main conclusions obtained are summarized as follows :(1) The small fatigue crack growth behavior in Ni-base superalloys are sensitive to the microstructures, such as grain boundaries, crystallographic slip plane and slip direction, and the size of gamma'precipitates. The intrinsic small fatigue crack growth resistance, in which the temperature dependence of elastic compliance and that of crack closure level are taken into account, decreases with temperature. The dissolution of gamma'precipitates by environmental effect closely contributes to the above temperature dependence.(2) The information on the long crack growth are not always applied to thesmall crack. The small cracks propagate even at lower stress intensity factor than the long crack threshold level. The similar phenomena are often found in other kinds of materials, such as the metal-matrix composites materials. These experimental evidences indicate the importance of the investigation of small crack growth behavior.(3) The diffecence between the long and small crack growth rates in the single crystal alloy are compensated by the crack closure phenomenon, but not in the polycrystalline alloy. The inhomogenity of strength properties as well as the difference of the fracture mode are closely related to the above difference between the long and small cracks.

在高温下研究了三种Ni-base Superalys，研究了小疲劳裂纹的生长行为。单晶合金，定向合金和pollycrystalline合金。温度和微观结构的影响还基于裂纹开放式和闭合行为的可操的研究。获得的主要结论总结如下：（1）Ni-base Superalloys中的小疲劳裂纹生长行为对微观结构对微观结构敏感，例如晶界，晶体边界，晶体界面滑移平面和滑动方向和尺寸的尺寸，尺寸和尺寸。内在的小疲劳裂纹生长抗性，其中弹性依从性和裂纹闭合水平的温度依赖性被考虑在内，随着温度而降低。通过环境效应的伽马释放量的溶解非常有助于上述温度依赖性。（2）关于长裂纹生长的信息并不总是应用于裂纹。小裂纹即使在较低的应力强度系数也比长裂纹阈值水平传播。类似的现象通常在其他种类的材料中，例如金属矩阵复合材料。这些实验证据表明研究了小裂纹生长行为的研究的重要性。（3）单晶合金中长和小裂纹生长速率之间的扩展是通过裂纹闭合现象来补偿的，但在多晶合金中没有补偿。强度特性的不孔子性以及断裂模式的差异与长裂纹和小裂纹之间的上述差异密切相关。