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超厚板TC4钛合金电子束焊接接头应力腐蚀敏感性
房卫萍1, 肖铁2, 张宇鹏1, 徐望辉1, 易耀勇1
1.广东省焊接技术研究所(广东省中乌研究院) 广东省现代焊接技术重点实验室, 广州 510650;2.中国科学院金属研究所, 沈阳 110016
摘要:
针对100 mm超厚板TC4钛合金电子束焊接接头,采用慢应变速率拉伸方法评价接头在人造海水中的应力腐蚀敏感性,分析接头的显微组织和断口形貌,对接头的腐蚀机制进行研究. 结果表明,室温条件下应变速率为ε=1×10-6 s-1时,母材在海水中未表现出应力腐蚀敏感性;焊缝上部、中部和下部具有轻微应力腐蚀敏感性. 焊缝在海水中发生阳极溶解,产生氢吸附,导致裂纹的萌生. 同时氢扩散诱导α'相界及α'相内发生位错塞积,进而使裂纹在更低的应力水平下发生扩展.
关键词:  电子束焊接  钛合金  应力腐蚀  显微组织  断口形貌
DOI:10.12073/j.hjxb.2019400324
分类号:TG456.3
基金项目:广州市项目(201907010010,201807010036);广东省科技项目(2018B090904004,2017A070701026,2016B070701025,2014B070705007);攀钢集团项目(2014外协03)
Stress corrosion crack sensitivity of ultra-thick TC4 titanium alloy electron beam welding joints
FANG Weiping1, XIAO Tie2, ZHANG Yupeng1, Xu Wanghui1, YI Yaoyong1
1.Guangdong Provincial Key Laboratory of Advanced Welding Technology, Guangdong Welding Institute, Guangzhou 510650, China;2.Institute of Metal Research Chinese Academy of Sciences, Shenyang 110016, China
Abstract:
Slow strain rate tensile method was adopted to evaluate the stress corrosion crack (SCC) sensitivity of 100 mm ultra-thick TC4 titanium alloy electron beam welded (EBW) joints under artificial seawater. The corrosion mechanism was studied by observing the microstructure and fracture morphology of the joint. The results showed that the base metal have no SCC sensitivity in seawater. However, the upper, middle and lower parts of the weld showed slight SCC sensitivity at room temperature under the condition of strain rate ε=1×10-6 s-1. In seawater, anodic dissolution accursed in the weld metal, which increased the Ti ion concentration in the solution at the crack tip, then, H atoms are evolved and absorbed at the crack tip. The diffused hydrogen then promotes dislocation emission and increases the dislocation density at the α' phase boundaries and in the α' phase. The crack initiation and propagation are results of the accumulation of highly hydrogen. At the same time, hydrogen enhances mobility of dislocations, then the crack propagates at a lower stress level.
Key words:  electron beam welding  titanium alloy  stress corrosion crack  microstructure  fracture morphology