Papers by Author: Alfredo Tolley

Abstract: A study on the microstructures developed during artificial aging of the 2024 alloy in nondeformed and 8% pre-deformed specimens is presented. The microstructural characterization was carried out using transmission electron microscopy (TEM), specifically, diffraction contrast and highresolution imaging. The S phase was found to precipitate heterogeneously on dislocations in both nondeformed and pre-deformed alloys. After the same artificial aging time, a larger density of S phase precipitates was obtained in the pre-deformed specimens. In non-deformed specimens, a high density of small nanometer-sized aggregates was found, that was absent in the pre-deformed specimens, that were identified as GP zones. To further analyze the small sized aggregates, artificially aged specimens with no previous deformation were also studied with Coincidence Doppler Broadening (CDB) of positron annihilation radiation. With this technique, information on the chemical environment around vacancy sites contained in the GP zones was obtained. Specifically, a composition close to (AlCu)2Mg was derived.