Microstructural evolution and interfacial crack corrosion behavior of double-sided laser beam welded 2060/2099 Al-Li alloys T-joints

Publication date: 5 December 2017
Source:Materials & Design, Volume 135
Author(s): Bing Han, Yanbin Chen, Wang Tao, Hao Li, Liqun Li
2060 and 2099 aluminum‑lithium (Al-Li) alloys are both the candidate structural materials for Chinese C919 aircraft fuselage panels and their related welding characteristics are greatly different from those of aviation aluminum alloys and need to be studied. Double-sided laser beam welding of 2-mm-thick 2060-T8 and 2099-T83 Al-Li alloys T-joints were successfully performed with 4047 wire. Microstructural evolution and interfacial micro-crack corrosion behavior within the weld were investigated. Microstructure analysis results showed that segregation in the weld was featured by the formation of T (LiAlSi), θ (Al2Cu) and eutectics at grain boundaries. By using focused ion beam (FIB), the interfacial layer between T-phase and α-Al matrix was found to be composed of alternately crystallized θ-phases and Al-Si eutectics. Micro-cracks were observed locating on the boundary between interfacial θ-phase and α-Al matrix. Corrosion test results indicated that the interfacial micro-crack dramatically accelerated the de-alloying in interfacial θ-phase and also the anodic dissolution in adjacent α-Al matrix. However, no corrosion feature was detected in the near surface of T-phase. The continuous selective dissolution of aluminum occurring in front of the micro-crack tip resulted in crack propagation along depth of the boundary between interfacial θ-phase and α-Al matrix.

Graphical abstract

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