(北京航空材料研究院，北京 100095)
摘 要: 研究TC4-DT钛合金在近门槛区的疲劳裂纹扩展速率和Paris区的转折点现象，并通过扫描电镜分析断口形貌和扩展路径，讨论等轴初生α相含量对TC4-DT钛合金疲劳裂纹扩展行为的影响规律。结果表明：随着等轴初生α相含量的减少，TC4-DT钛合金在近门槛区的疲劳裂纹扩展速率显著降低，并在da/dN—ΔK曲线的Paris区逐渐呈现转折点现象，转折点位置所对应的DKt值逐渐增大；片层组织在近门槛区的裂纹扩展路径曲折，疲劳裂纹扩展速率显著降低。
关键字: 损伤容限；TC4-DT钛合金；近门槛区；疲劳裂纹扩展；转折点
（Beijing Institute of Aeronautical Materials, Beijing 100095, China）
Abstract:The fatigue crack growth rate and the turning point in Paris region of the curves of the TC4-DT titanium alloy was compared. The effect of the content of primary α phase on fatigue crack propagation behavior of lamellar microstructure of TC4-DT titanium alloy was discussed by scanning electron microscopy (SEM) analyses of fracture morphology and crack propagation paths. The results show that there occurs lower fatigue crack growth rate with decrease in the content of primary α phase, with appearance of the turning point in Paris region and increase in the ΔKt of turning point. The lamellar microstructure exhibits tortuous crack paths and fatigue crack propagation resistance, which indicates that the lamellar structure has better damage tolerance compared with bimodal structure.
Key words: damage tolerance; TC4-DT titanium alloys; near-threshold zone; fatigue crack propagation; turning point
