Corrosion behavior of 2195 aluminum-lithium alloy stir friction welded joints under tropical marine atmospheric conditions

For 2195 aluminum-lithium alloy exposed to tropical marine atmospheric conditions of service, its corrosion behavior was researched through metallographic observation, transmission electron microscopy (TEM) observation, corrosion morphology observation and mechanical properties testing. The results showed that corrosion of heat affected zone was stronger than that of weld, which was due to the presence of T1 phase in heat affected zone, while weld did not exist T1 phase. Main corrosion form of welded parts was spalling corrosion. After 3 months of exposure, welded parts appeared skinning phenomenon. After 6 months of exposure, area of corrosion pits expanded and they were connected into a corrosion zone. Meanwhile, corrosion pits began to become deeper, tensile properties of welded parts was significantly reduced. After 12 months of exposure, depth of corrosion pits reached 22.7 μm. Tensile strength and elongation of welded joints were significantly reduced, tensile strength was reduced from 449.45 MPa after 3 months of exposure to 373.25 MPa after 12 months of exposure, and elongation was reduced from 11.254% to 7.756%. In corrosion process, change rate of corrosion pits of weld at the deepest depth remained stable, about 5 μm/month.Highlights: Corrosion behavior of 2195 aluminum-lithium alloy FSW joints and change process of their mechanical properties were studied through corrosion experiments exposed to real tropical marine atmospheric conditions, which provided a reference for the use of this joint in specific environments.