REVERSING SENSITIZATION OF NATURALLY EXFOLIATED 5456-H116 ALUMINUM ALLOYS

Authors

Ren-Yu Chen, School of Defense Science, Chung Cheng Institute of Technology, National Defense University, Taoyuan, Taiwan, R.O.C.Follow
Cheng-Chyuan Lai, Department of Mechatronic, Energy and Aerospace Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan, Taiwan, R.O.C.

Abstract

5456-H116 Al-Mg alloy has been broadly used in the U.S. Navy in order to meet the demand of reducing ship hull weight while considering high specific strength, corrosion resistance, and weldability. A particular concern of these alloy is sensitization, which causes it to be sensitized when highly anodic β phase (Al3Mg2) is precipitated at grain boundaries especially in service exceeding 65~200°C, leading to intergranular corrosion (IGC), exfoliation and stress corrosion cracking (SCC). This study investigated the reversal of sensitization of a naturally exfoliated 5456-H116 alloy plate by planned heating treatment with a short exposure to 250°C. The properties of sensitized specimens of 5456-H116 were investigated using microhardness testing, electrochemical measurements, Nitric Acid Mass Loss Testing (NAMLT), optical microscopy, and Scanning Electron Microscopy (SEM). The results reveal that the corrosion resistance of the stabilized specimens approached those of the unsensitized plates, and their mechanical strength was not adversely affected during the recovery process. Therefore, in-service plates can be refurbished by stabilizing heat treatment rather than replacement, potentially reducing maintenance costs.

Recommended Citation

Chen, Ren-Yu and Lai, Cheng-Chyuan (2014) "REVERSING SENSITIZATION OF NATURALLY EXFOLIATED 5456-H116 ALUMINUM ALLOYS," Journal of Marine Science and Technology: Vol. 22: Iss. 4, Article 6.
DOI: 10.6119/JMST-013-0521-4
Available at: https://jmstt.ntou.edu.tw/journal/vol22/iss4/6