Investigation of dealloying by ultra-high-resolution nanotomography

Sequential sectioning and sequential imaging by scanning electron microscopy have been employed to obtain three-dimensional images of an AA2024-T3 aluminium alloy after exposure to sodium chloride solution. The three-dimensional arrangement of intermetallic particles within the alloy was disclosed, indicating that groupings of intermetallics are preferential sites for corrosion initiation due to the combined presence of defects such as cracks or voids and local differences in electrochemical potential. Three-dimensional imaging enabled the study of the dealloying process occurring on the S-phase particles (Al-Cu-Mg) during corrosion, revealing the details of a copper-rich sponge-like structure. Initially, dealloying proceeds by initial formation of a copper-rich nanoporous layer containing significant amounts of residual aluminium and magnesium. Subsequently, the layer dealloys further, increasing the free volume of the porous structure. At later stages of dealloying, some copper metal clusters detach from the substrate and oxidize. Copyright ?? 2012 John Wiley & Sons, Ltd. Copyright ?? 2012 John Wiley & Sons, Ltd.