Fractographic analysis of fatigue crack initiation and propagation in CP titanium with a bimodal harmonic structure
Fractographic analysis of fatigue crack initiation and propagation in CP titanium with a bimodal harmonic structure
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DOI：
10.1016/j.msea.2018.01.054
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发表时间：
2018-02
期刊：
影响因子：
6.4
通讯作者：
Yuhei Nukui;H. Kubozono;S. Kikuchi;Y. Nakai;A. Ueno;M. Kawabata;K. Ameyama
中科院分区：
文献类型：
--
作者：
Yuhei Nukui;H. Kubozono;S. Kikuchi;Y. Nakai;A. Ueno;M. Kawabata;K. Ameyama
商业纯钛（CP）具有双峰谐波结构，其定义为由细晶粒网络包围的粗晶粒区域，通过强化机械研磨粉末来提高强度和延展性。为了确定双峰谐波结构CP钛的疲劳性能，在环境条件下，在应力比为0.1的条件下进行了四点弯曲疲劳试验。利用扫描电镜（SEM）和电子背散射衍射（EBSD）对断口进行了分析，在断口形貌和晶体形貌的基础上，确定了疲劳小裂纹的萌生和扩展机理。与由接收的初始粉末制备的烧结致密体相比，其抗疲劳裂纹萌生能力有所提高，这是由于机械铣削过程中晶粒细化所致。穿晶断裂主要发生在基面垂直于加载方向的粗晶处。谐波结构CP钛的疲劳裂纹路径不受微观组织的影响。
Commercially pure (CP) titanium with a bimodal harmonic structure, which is defined as coarse grained regions surrounded by a network of fine grains, was fabricated by consolidating mechanically milled powders to improve both strength and ductility. In order to determine the fatigue properties of bimodal harmonic structured CP titanium, four-point bending fatigue tests were conducted at a stress ratio of 0.1 under ambient conditions. The fracture surfaces were analyzed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) to identify the mechanisms of small fatigue crack initiation and propagation on the basis of fractography and crystallography. The fatigue crack initiation resistance was increased compared to sintered compacts fabricated from as-received initial powders, which was attributed to grain refinement during mechanical milling. Transgranular fracture occurred from coarse grains with a basal plane perpendicular to the loading direction. The fatigue crack path in harmonic structured CP titanium was not influenced by the microstructure.