TC11钛合金电子束焊接接头超高周疲劳性能

采用天津大学自行研制的TJU-HJ-I型超声疲劳试验系统研究了TC11钛合金电子束焊焊接接头的超高周疲劳性能. 试验结果表明，TC11钛合金电子束焊接接头在107周次以上仍然会发生疲劳失效，S-N曲线呈现连续下降的趋势，没有明显的转折. 试件的断裂位置大多数为母材处，焊缝和热影响区的疲劳性能要比母材好，这与焊接接头的微观组织有关. 通过SEM对超声疲劳断口形貌进行观察发现，断裂试件的疲劳裂纹大部分在表面萌生，然而在应力范围较低时，疲劳裂纹的萌生位置有从表面转向次表面的趋势.

Properties of very-high-cycle fatigue of TC11 titanium alloy EBW welded joints

Ultrasonic fatigue tests are carried out to investigate very-high-cycle fatigue property of TC11 titanium alloy electron beam welding joint. The results show that fracture still occurs in the TC11 titanium alloy welded joints after 107 cycles, and the S-N curve presents a continuously decreasing shape. No obvious inflection point can be found in S-N curve. Most of the specimens fracture in the base metal and fatigue properties of weld joint and HAZ are better than the base metal due to the microstructure of welded joint. The morphology of specimen is observed by scanning electron microscope. It is proved that most of fatigue cracks initiate at the surface. However, fatigue crack initiation site transforms from surface to subsurface in the longer life regime.