(北京航空航天大学 材料科学与工程学院 空天材料与服役教育部重点实验室，北京100191)
摘 要: 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Smax—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。
关键字: TC18钛合金；疲劳性能；断口形貌；疲劳源；疲劳裂纹扩展区
TC18 titanium alloy lugs
（Key Laboratory of Aerospace Materials and Performance, Ministry of Education,
School of Materials Science and Engineering, Beihang University, Beijing 100191, China）
Abstract:The fatigue behavior of straight lugs of TC18 titanium alloy is studied. The fatigue Smax—N curves are tested at different heat treatment status and average stresses. The typical fatigue fracture surfaces are observed and analyzed by SEM (scanning electron microscope). The results show that the heat treatment status and the average stress have obvious influence on the fatigue limit; the fatigue limit of the samples, annealed after machining, is upper at the same average stress; the fatigue limit will be longer when the average stresses are higher at the same annealed status; the fatigue crack mainly initiates at inclusion, surface defect or inner defect on sub-surface; the crack propagation rate will be larger when the load stress is higher in the crack propagation region.
Key words: TC18 titanium alloy; fatigue behavior; fractograph; fatigue crack initiation; fatigue crack propagation
