Hardening nanostructures in an AlZnMg alloy

A. DUPASQUIER; R. FERRAGUT; M. M. IGLESIAS; M. MASSAZZA; G. RIONTINO; P. MENGUCCI; G. BARUCCA; C. E. MACCHI; A. SOMOZA

PHILOSOPHICAL MAGAZINE A

Taylor and Francis

Año: 2007 vol. 87 p. 3297 - 3323

0141-8610

The formation of nanoscale and sub-nanoscale solute aggregates (clusters,Guinier–Preston zones and precipitates) in an AlZnMg alloy (Al–2.1 at.%Zn–1.5 at.% Mg) has been followed by a combination of experimental techniqueswith the aim of correlating the properties of the aggregates with their thermalhistory. The choice of thermal treatments was guided by the results ofmechanical and calorimetric characterizations, supported by transmissionelectron microscopy for the identification of the morphology of the aggregates.Positron annihilation spectroscopy (using two variants of this technique,coincidence Doppler broadening and lifetime spectroscopy) was adopted fordetermining the local chemistry in the proximity of open volume defects.The geometrical parameters of the distribution (size, volume fraction, numericaldensity of the solute aggregates) were obtained by small-angle X-ray scattering.The results of the investigation provide new information regarding: twofamilies of vacancy-rich clusters formed during or immediately after quenching;Guinier–Preston zones formed at 95C after room-temperature pre-ageing;growth of 0 and phases at 150C; solute clusters formed at room-temperaturein conditions of secondary ageing after preliminary heating at 150C.