The hydrogenated CT specimens were adopted to measure the fatigue crack propagation rate (da/dN) of TC4 alloy electron beam welded joints at room temperature, and the fracture surface morphologies of specimens as well as the microstructures of joints were observed. The results indicated that the da/dN of hydrogenated base metal specimens were higher than the non-hydrogenated ones in near-threshold stage and rapid rupture stage, but the specimens with various hydrogen contents were little differed from each other, and hydrogen showed little effects on da/dN in stable crack propagation stage (Paris stage). During the whole crack propagation process,the da/dN of hydrogenated weld bead specimens was obviously enhanced and increased with the increment of hydrogen content. The analysis results of fracture surface morphologies showed that the crack propagation was promoted by hydrogen owing to the increase of brittleness of titanium alloy. In Paris stage, the transition of microstructure of the material has an apparent effect on da/dN, and the acicular martensite at the weld bead zone of electron beam welded joint has a higher resistance to crack propagation than lamellar α+β structure.%采用充氢CT试样对TC4钛合金电子束焊接头的室温疲劳裂纹扩展速率进行了测定,并对试样断口和接头各区显微组织进行了观察.试验结果表明:充氢母材试样在低速扩展区和失稳扩展区的da/dN相对于未充氢试样有明显的提高,但不同氢含量之间差别不大,在稳态扩展区(Paris区),氢对da/dN的影响很小.充氢焊缝试样在整个裂纹扩展过程中的da/dN明显提高,且随着氢含量的增加而增加.断口分析结果表明氢的加入使得材料脆性增大,促进了裂纹的扩展.在Paris区,组织结构的转变对da/dN的影响显著,电子束焊接头焊缝的针状马氏体组织比层片状α+β组织具有更高的抵抗裂纹扩展的能力.
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