复合细化超细晶工业纯钛高周疲劳性能研究

High-Cycle Fatigue of Ultra-fine Grained Commercial Purity Titanium by Combined refining process

摘要:

室温下,超细晶工业纯钛光滑试样在加载频率f=25 Hz、应力比R=-1的条件下进行高周应力疲劳测试,拟合超细晶工业纯钛应力幅σ_a与疲劳断裂循环周次N_f之间的关系曲线,并对疲劳断口形貌进行观察分析。结果表明：200 ℃退火60 min超细晶工业纯钛的疲劳极限值σ_-1为376.5 MP,比未退火超细晶工业纯钛的疲劳极限值提高56.5 MPa。疲劳裂纹源萌生于超细晶工业纯钛的表面, 200 ℃退火60 min超细晶工业纯钛的疲劳辉纹间距较小,疲劳裂纹不易扩展,室温疲劳性能优良。

Abstract:

Stress-controlled high-cycle fatigue performance of ultra-fine grained commercial purity titanium (UFG CP Ti) was conducted with a loading frequency of 25 Hz and a stress ratio R=-1 at room temperature. The relation between stress amplitude and cycle numbers to failure was fitted, and the fatigue fracture surface of UFG CP Ti specimen was also investigated. The results showed that the fatigue limit of annealed UFG CP Ti specimen at 200℃ for 60 min was 376.5 MPa, which increased 56.5 MPa compared with the unannealed one. Moreover, the fatigue cracks mainly initiated from the surface of fatigue specimen. The annealed UFG CP Ti specimen exhibited the smaller fatigue striation spacing and lower crack propagation rate than the unannealed one, indicating a higher room temperature fatigue performance.