Microstructural characterization of a commercial Al–Cu–Mg alloy combining transmission electron microscopy and positron annihilation spectroscopy.

A. TOLLEY; R. FERRAGUT; A. SOMOZA

PHILOSOPHICAL MAGAZINE

TAYLOR & FRANCIS LTD

Año: 2009 vol. 89 p. 1095 - 1110

1478-6435

Transmission electron microscopy and positron annihilation spectroscopytechniques were used to characterise the microstructure of the 2024 Al–Cu–Mg commercial alloy artificially aged with and without pre-deformation.In non-deformed samples, a very dense dispersion of small, needle-shapedparticles, with mean size in the order of the nanometres, was observedhomogeneously distributed in the matrix, together with a coarse distributionof S-phase precipitates. In pre-deformed samples, the needle-shapeparticles were not seen, only a high density of S-phase precipitatesnucleated on dislocations. The needle-shaped particles were identified assolute-rich Guinier–Preston–Bagaryatski (GPB) zones by combiningcoincidence Doppler broadening positron annihilation measurementswith TEM imaging. The relationship between the microstructure andmeasurements of hardness and positron lifetime evolution during artificialageing is also discussed.