Distribution of Internal Crack Initiation Sites in High-cycle Fatigue for Titanium Alloys
Distribution of Internal Crack Initiation Sites in High-cycle Fatigue for Titanium Alloys
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DOI：
10.2355/isijinternational.37.1237
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发表时间：
1997-12
影响因子：
1.8
通讯作者：
H. Yokoyama;O. Umezawa;K. Nagai;Toshiyuki Suzuki
中科院分区：
文献类型：
--
作者：
H. Yokoyama;O. Umezawa;K. Nagai;Toshiyuki Suzuki
为了阐明高周疲劳过程中裂纹萌生位置的微观分布规律，对不同微观组织的α-β或近α钛合金进行了液氮中的疲劳试验。在77 K下，内部裂纹的萌生超过105个循环。裂纹起始点为晶面或晶面集合体，均为α晶粒穿晶裂纹。在等轴α组织中，起始点明显地局限在试样表面附近（即距试样表面10-200 μm）。在针状α结构中，位置或多或少靠近试样表面，并且还观察到更多的内部情况，这与较大的起始部位尺寸有关。而在拉长α组织中，断裂位置则从试样表面附近向断口中心分散。评估了内部裂纹萌生点的大小，并从循环应力及其大小的角度讨论了这些位置。
In order to clarify how the internal crack initiation site distributes according to microstructure in high-cycle fatigue, α-β or near α titanium alloys with various microstructure were subjected to fatigue test in liquid nitrogen. The internal crack initiation occurred longer than 105 cycles at 77 K. The initiation site was a facet or its aggregate which originated from α grain transgranular cracking in each material. In equiaxed α structures, the location of initiation site was obviously restricted to near the specimen surface (i.e. 10-200 μm deep from the specimen surface). In acicular α structures, the location was more or less near the specimen surface and more interior cases were also seen, which were associated with a larger initiation site size. In elongated α structure, on the contrary, the location was scattered from the vicinity of specimen surface to the center in fracture surface. The size of the internal crack initiation sites was evaluated, and the location of the sites was discussed from the viewpoints of the cyclic stress and their size.