时效处理对铝锂合金电子束焊接头耐蚀性能的影响

Effect of Aging Treatment on Corrosion Resistance of Al-Li Alloy Joint Welded by Electron Beam Welding

摘要:

对铝锂合金电子束焊接头进行焊后热处理,研究了时效处理前后接头各区域的晶间腐蚀、剥蚀和电化学腐蚀行为。结果表明,接头经过时效处理后,焊缝晶界析出的T₁(Al₂CuLi)相数量增加,并且形成了明显的晶界无沉淀带(Precipitate Free Zone,PFZ)。焊态下接头未出现晶间腐蚀,热影响区和母材区均出现了孔蚀；焊后时效处理增大了接头的晶间腐蚀倾向,热影响区同时发生了孔蚀和晶间腐蚀,母材区出现了严重的晶间腐蚀。焊态下焊缝和热影响区均具有优异的抗剥蚀能力,母材区对剥蚀的敏感性较高；焊后时效处理可提高接头母材区的抗剥蚀能力,但会增大热影响区的剥蚀敏感性。电化学腐蚀测试表明,与时效后的接头焊缝相比,焊态下焊缝的自腐蚀电位较高,腐蚀电流密度小,具有相对较好的耐蚀性。

Abstract:

The post-weld heat treatment(PWHT) is carried out to Al-Li alloy joints welded by electron beam welding(EBW), and the behaviour of intergranular corrosion(IGC), exfoliation corrosion(EXCO) and electrochemical corrosion of different zones of welded joint before and after PWHT are investigated. Results show that the quantity of phase T₁(Al₂CuLi) in grain boundry of weldment increased after solution and aging treatment, and the obvious precipitate free zone(PFZ) generated to grain boundry. The IGC does not occur to joint in as-welded(AW) condition, while the pitting corrosion occurs to both heat-affected zone(HAZ) and base metal of welded joint. The susceptibility to IGC of joint increased after aging treatment, both the pitting corrosion and IGC occurred to HAZ, and the severe IGC produced to base metal. It has excellent EXCO resistance for both weld metal and HAZ in AW condition, while the susceptibility to EXCO is higher for base metal. The EXCO resistance can be improved to base metal after aging treatment, however the susceptibility to EXCO will increase to HAZ. Results of electrochemical corrosion measurement show that, compared to the weldment after aging treatment, the self-corrosion potential of weldment is a little higher in AW condition, and its density of self-corrosion current is lower, consequently, it has the relatively better corrosion resistance.