Effect of precipitate evolution on corrosion behavior of friction stir welded joints of AA2060-T8 alloy
(1. AVIC Manufacturing Technology Institute, Beijing 100024, China;
2. State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004, China;
3. Beijing Higher Institution Engineering Research Center of Energy Engineering Advanced Joining Technology, Beijing Institute of Petrochemical Technology, Beijing 102617, China)
2. State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004, China;
3. Beijing Higher Institution Engineering Research Center of Energy Engineering Advanced Joining Technology, Beijing Institute of Petrochemical Technology, Beijing 102617, China)
Abstract: Friction stir welding was used to join two AA2060-T8 plates, and then the effect of precipitate evolution on microstructure and corrosion behavior of the joint was investigated. The evolution of precipitates on the top surface of the joint was characterized by scanning electron microscopy and transmission electron microscopy. The corrosion behaviors of different regions in the joint were investigated by an electrochemistry method and an alternating salt spray exposure. The corrosion was mainly dependent on the nature of precipitates in each region of the joint. The shoulder affected zone had the worst corrosion resistance as a result of the re-dissolved of θ′(Al2Cu), T1(Al2CuLi) and δ′(Al3Li) phases, the formation of intergranular precipitates and precipitate-free zones. However, the thermomechanically affected zone had a slightly improved corrosion resistance because it had no intergranular precipitates. The heat affected zone and base metal had the best corrosion resistance.
Key words: 2060-T8 aluminum alloy; friction stir welding; precipitate; microstructure; micro-electrochemical characteristics