Surface severe plastic deformation induced solute and precipitate redistribution in an Al-Cu-Mg alloy

Abstract

The precipitate and solute distribution in a surface severely plastically deformed Al-Cu-Mg alloy were revealed by means of transmission electron microscopy and atom probe tomography. Accompanying gradient grain structure, there is a gradient precipitate architecture which evolves from undeformed needle-like S (Al2CuMg) precipitates to shear-deformed and fragmented S precipitates along low angle dislocation boundaries within coarse grains, to reprecipitated Gunier-Preston-Bagaryatsky (GPB) zones and S precipitates in lamellar nanograins, and to completely dissolved and segregated solutes to nanograin boundaries. Dislocation activities induced precipitate dissolution and promoted solute diffusion are two concomitant processes during precipitate and solute redistribution. The variation of precipitate crystallography, including orientation relationship deviation and coherency loss between S precipitates and Al matrix, was attributed to local changes in strain fields around undissolved S precipitates and in nucleation environment for reprecipitated S phase.