• CN：11-2187/TH
  • ISSN：0577-6686
机械工程学报

机械工程学报 ›› 2015, Vol. 51 ›› Issue (12): 69-75.doi: 10.3901/JME.2015.12.069

• 材料科学与工程 • 上一篇    下一篇

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TC21钛合金电子束焊接接头超高周疲劳行为研究

马婧, 赵子华, 聂宝华, 郑志腾, 张峥   

  1. 北京航空航天大学材料科学与工程学院
  • 出版日期:2015-06-20 发布日期:2015-06-20
  • 基金资助:
    国家自然科学基金资助项目(51101009)

Research on Very High Cycle Fatigue Behavior of the Electron Beam Weldment for TC21 Titanium Alloy

MA Jing, ZHAO Zihua, NIE Baohua, ZHENG Zhiteng, ZHANG Zheng   

  1. Institute of Materials Science and Engineering, Beihang University, Beijing 100191
  • Online:2015-06-20 Published:2015-06-20

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摘要： 采用超声疲劳试验方法(20 kHz)，研究TC21钛合金电子束焊接接头的超高周疲劳性能与断裂机理。结果表明，TC21钛合金电子束焊接接头的疲劳性能要远低于母材的疲劳性能。在短寿命阶段，电子束焊接接头和母材的疲劳裂纹均在表面萌生；当寿命增大时，两者疲劳裂纹的萌生位置均由表面转向内部，母材的疲劳裂纹主要萌生于内部显微组织，而电子束焊接接头疲劳裂纹主要萌生于内部焊接气孔缺陷。当寿命较长时，疲劳源区会出现“鱼眼”形貌特征，源区附近有白色颗粒状细晶区，即细晶区(Fine granular area, FGA)，其应力强度因子在2.90～3.33 MPa•m1/2，与疲劳寿命没有直接关系，可以认为是疲劳裂纹扩展门槛值。此外，基于AKINIWA小裂纹扩展理论，定量分析气孔尺寸与TC21焊接接头疲劳极限、疲劳应力的关系。

关键词: TC21钛合金, 超高周疲劳, 电子束焊接接头, 气孔尺寸

Abstract: The very high cycle fatigue properties and fracture mechanism of the electron beam weldment for TC21 titanium alloy are investigated by the ultrasonic fatigue testing method. The results show fatigue strength of electron beam weldment is much lower than that of base metal. In the shorter life regime, fatigue crack initiates on the surface for both base metal and electron beam weldment. However, in the longer life regime, the site of fatigue crack initiation transforms from surface to interior. Fatigue crack mainly initiates at internal microstructure for base metal, while fatigue crack initiates at weld pore for electron beam weldment. When fatigue life is longer, the initiation zone would appear "fish eye" morphology and the area near initiation zone appears white granular characteristics named FGA. The stress intensity factor ranges from 2.90 MPa•m1/2 to 3.33 MPa•m1/2 at the front of FGA is regarded as the threshold value of internal crack propagation. The relationship among fatigue life, fatigue stress and pore size is discussed based on the short crack propagation theory proposed by AKINIWA.

Key words: electron beam weldment, pore size, TC21 titanium alloy, very high cycle fatigue

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