Abstract
In the present work, the microstructure, electrochemical behavior and localized corrosion of the AA2198-T851 Al-Cu-Li alloy were studied. The microstructure was correlated with corrosion results obtained by immersion, gel visualization and scanning electrochemical microscopy (SECM) tests. Immersion and gel visualization tests showed high kinetics of corrosion attack during the first hours of immersion. SECM analyzes by means of surface generation/tip collection (SG/TC) mode detected hydrogen evolution generated during spontaneous corrosion from severe localized corrosion (SLC) sites on the metal surface. SECM results revealed sites of intense hydrogen evolution after 2 h of immersion and increased amounts of corrosion products after 4 h of immersion. Hydrogen evolution sites detected by SECM were associated with severe localized corrosion (SLC).
Highlights
Al-Cu-Li alloys are high-performance materials employed in aircraft industry due to their characteristics
The results revealed that the propagation of severe localized corrosion (SLC) is crystallographic and associated with the slip bands in the individual grains of the alloy
The grains are equiaxed suggesting that recrystallization takes place, during the T851 treatment due to alloy deformation above of the cold working temperature[56]
Summary
Al-Cu-Li alloys are high-performance materials employed in aircraft industry due to their characteristics (low density, high mechanical resistance, high tenacity, high-temperature resistance, weldability and good response to natural aging). In order to maximize and ensure those properties, processing of alloy needs to select accurately the thermomechanical processing routes and optimize the chemical composition[1,2,3,4,5,6]. This is important because the final microstructure of the alloy directly influences its performance. Precipitation and distribution of the nanosized particles occurs during thermomechanical processes[7] These particles present different contributions to the alloy mechanical properties: only the nano-sized particles contribute actively by improving the alloy mechanical resistance. High level of deformation increases the number of dislocations leading to a high T1 phase density and improved mechanical resistance
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