Precipitation kinetics, mechanical strength and electrical conductivity of AlZnMgCu alloys

The aging of AlZnMgCu alloys in a temperature range where the metastable phase eta' precipitates homogeneously, is examined with a three-fold point of view using the microstructural parameters measured previously by in situ small angle X-ray scattering experiments. The precipitation kinetics is first analysed and the late LSW coarsening stage is unambiguously characterized. The yield stress is then quantified in terms of precipitate dislocations interactions. Shearing of the transition phase eta' and possibly coherency strains control the initial hardening increase, whereas eta' or eta precipitate Orowan by-passing explains the yield-stress decrease occurring during the coarsening stage. Finally, the correlation with the electrical conductivity is established on the basis of a semi-phenomenological two-phase model of electron scattering, showing that the late conductivity increase can be attributed to the precipitate coarsening at constant volume fraction. Copyright (C) 1996 Acta Metallurgica Inc.