【摘要】 钛合金广泛应用于军事航空领域 ,但是一些钛合金在焊接条件下 ,焊缝会产生氢致延迟裂纹 ,其致裂机理尚不十分清楚。通过充氢CT(Compacttension)试件的恒载拉伸试验 ,研究了氢浓度对Ti5 5合金电子束焊缝裂纹尖端应力强度因子门槛值Kth及裂纹扩展速率da/dt的影响规律 ,分析了氢致延迟裂纹扩展的机理。结果表明 ,氢在Ti5 5合金焊缝中的固溶度约为 79× 10 -4%。当充氢浓度C0 低于 79× 10 -4%时 ,随着焊缝氢浓度C0 的增大 ,裂纹开始扩展的应力强度因子门槛值Kth迅速减小 ,而裂纹扩展速率da/dt随着C0 的增大而增大 ;C0 为 79× 10 -4%时 ,Kth为最小值并呈恒值特征。裂纹尖端应力场诱导氢原子扩散导致氢化物TiH2 析出是Ti5 5合金电子束焊缝氢致延迟裂纹扩展的主要机制更多还原

【Abstract】 Titanium alloys are widely used in the military aerospace region.However,hydrogen induced delayed cracks could occur in the weld of some titanium alloys in certain welding condition.And the mechanism concerning hydrogen induced delayed crack is not clear.In this paper,the pre cracked CT specimens of Ti55 charged with hydrogen were strained in tension and the effect of hydrogen content was studied on the threshold stress intensity factor K th ,and the crack growth rate d a /d t ;at a crack tip in EBW of Ti55 alloy.Meanwhile,the mechanism of hydrogen induced delayed crack was analyzed.The results indicate that the solid solubility of hydrogen in Ti55 is about 79×10 -4 %.At hydrogen contents below 79×10 -4 % K th decreases with increasing hydrogen content,whereas d a /d t increasess as the hydrogen content increases.When hydrogen content gets to about 79×10 -4 %, K th reaches the minimum and keep an invariable value.The mechanism of hydrogen induced delayed crack in EBW of Ti55 alloy is the diffusion of hydrogen up a stress gradinent to form hydride TiH 2 which precipitates at the crack tip.更多还原