超厚板TC4钛合金电子束焊接接头应力腐蚀敏感性

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.

Stress corrosion crack sensitivity of ultra-thick TC4 titanium alloy electron beam welding joints

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.