Abstract
We carried out a comparative study on both the stress corrosion response and corrosion damage characteristics of aluminum alloy 2219, both the base material and a friction stir welding (FSW) counterpart upon exposure to exfoliation corrosion (EXCO) solution. The results reveal that the test specimen containing an FSW joint reveals better electrochemical corrosion resistance than that taken from the base metal. When test specimens upon exposure to EXCO solution are concurrently subjected to a tensile stress, since the mechanical properties of the FSW joint are lower than the base metal, a test specimen containing an FSW joint is more easily prone to the early initiation of fine microscopic cracks. This makes the test specimen containing the FSW joint to be less resistant to stress corrosion damage than that taken from the base metal for the various levels of applied stress and exposure time to EXCO solution. The average corrosion depth of the test specimen containing the FSW joint is less than that of the base metal, while the maximum corrosion depth of it is greater than that of the base metal. This reveals that test specimen containing the FSW joint is more susceptible to damage and degradation than test specimen taken from the base metal.
Highlights
Aluminum alloy 2219 is an Al-Cu-Mn alloy that is receptive to heat treatment
Friction stir welding (FSW) is a new material joining technology invented by The Welding Institute (TWI) in 1991
Results of the tests reveal that corrosion of the test specimen containing the friction stir welding (FSW) joint and test specimen of the base metal gradually increases with an increase in the duration of exposure to the aqueous environment
Summary
Aluminum alloy 2219 is an Al-Cu-Mn alloy that is receptive to heat treatment. This alloy offers the characteristics of low density, high specific strength (σ/ρ), good heat resistance coupled with high sensitivity to stress corrosion. The workpiece is heated to below the melting point and in a plastic state under the action of heat, and the solid-phase connection of the material is realized under the action of stirring and clamping force [1]. Compared one-on-one with the traditional fusion welding methods, the FSW joint of an aluminum alloy has a more homogeneous microstructure coupled with the presence of fewer defects [2,3]. During FSW, the chosen aluminum alloy is subjected to stirring caused by a stirring needle coupled with heat input. This favors the occurrence of plastic deformation at the fine microscopic level coupled with dynamic recrystallization and a resultant change to the microstructure.
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