Initial Intergranular Cracking of Ni-Base Superalloys Due to the Degradation of the Crystallinity of Grain Boundaries Under Creep-Fatigue Loading
Initial Intergranular Cracking of Ni-Base Superalloys Due to the Degradation of the Crystallinity of Grain Boundaries Under Creep-Fatigue Loading
复制标题
蠕变疲劳载荷下晶界结晶度退化导致镍基高温合金的初始晶间裂纹
DOI：
10.1007/978-3-030-47883-4_58
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Miura Hideo
中科院分区：
文献类型：
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作者：
Suzuki Wataru;Luo Yifan;Ishihara Kenta;Suzuki Kens;Miura Hideo
利用电子背散射衍射（EBSD）分析，阐明了镍基高温合金617在高温蠕变疲劳载荷下寿命急剧下降的机理。通过间歇蠕变疲劳试验和EBSD分析监测了材料的退化过程。通过EBSD分析获得的图像质量（IQ）值，定量分析了晶粒和晶界结晶度的变化。IQ值表示空位、位错、局部应变等缺陷的密度，IQ值的降低对应于观察区域的结晶度的降低。在蠕变疲劳载荷作用下，细小孔洞的积累加速，不仅导致IQ值急剧下降，而且导致晶界强度急剧下降。当晶界结晶度下降到临界值时，晶界处位错和空洞的局部聚集导致结晶度下降，从而导致沿晶开裂。
The mechanism of the drastic decrease in the lifetime of Ni-base superalloy, Alloy 617 under creep-fatigue loading at elevated temperatures was clarified by using EBSD (Electron Back-Scatter Diffraction) analysis. The degradation process was monitored by using an intermittent creep-fatigue test and EBSD analysis. The change of the crystallinity of grains and grain boundaries was quantitatively analyzed by using the image quality (IQ) value obtained from the EBSD analysis. The IQ value indicated the density of defects such as vacancies, dislocations, local strain, and so on. The decrease in the IQ value corresponded to the decrease in the crystallinity of the observed area. The accumulation of fine voids was found to be accelerated under the creep-fatigue loading, and it caused the drastic decrease of not only the IQ value, but also the strength of the grain boundaries. Intergranular cracking started to occur when the crystallinity of grain boundaries decreased to the critical value due to the degradation of the crystallinity caused by the local accumulation of dislocations and voids around the grain boundaries.