Investigation of dealloying of S phase (Al2CuMg) in AA 2024-T3 aluminium alloy using high resolution 2D and 3D electron imaging

High-resolution 2D and 3D electron microscopy have been employed to investigate the dealloying of S phase (Al2CuMg) particles in an AA 2024-T3 aluminium alloy. Preferential dissolution of magnesium and aluminium produced a sponge-like remnant with nanosize porosity and a copper-rich remnant network. The dealloyed S phase remnant retains a tetragonal structure with a smaller lattice parameter than the S phase. Metallic copper nanoparticles, constituting 4-8% of the dealloyed remnant, are present at the intersections of remnant branches. At the surface of the remnant, a copper layer of ∼2 nm thickness is formed, which terminates further dissolution of the less noble elements.