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对TC18钛合金直耳片的疲劳性能进行研究,测试在不同处理状态及平均应力水平下耳片的疲劳S_(max)—N曲线,并利用扫描电镜(SEM)对疲劳试样断口的典型裂纹源形貌和裂纹扩展形貌进行观察分析。结果表明:热处理状态和平均应力对耳片疲劳寿命有较大影响;在相同的平均应力下,机械加工后退火处理的试样具有较高的疲劳寿命;在相同退火处理状态下,平均应力水平高,疲劳寿命长;疲劳裂纹主要在夹杂物、材料表面缺陷及次表面内部缺陷等处形成;在裂纹扩展区,对试样加载的应力水平越高,裂纹扩展速率也越大。
The fatigue properties of TC18 titanium alloy straight ear were studied, and the fatigue S_ (max) -N curve of the ear was tested under different processing conditions and average stress level. The typical crack of the fatigue crack tip was observed by scanning electron microscope (SEM) Source morphology and crack growth morphology were observed and analyzed. The results show that the heat treatment state and the average stress have a significant effect on the fatigue life of the ear. Under the same average stress, the samples annealed after mechanical processing have higher fatigue life. Under the same annealing condition, the average stress level High fatigue strength and long fatigue life. The fatigue cracks are mainly formed by inclusions, material surface defects and internal defects on the subsurface. In the crack propagation zone, the higher the stress level on the specimen, the larger the crack propagation rate.