Precipitation behavior of β-phase in 5083 aluminum alloy

A commercial 5083 aluminum alloy was aged at 453 K for an extended time in order to study the changes in the microstructures. In this alloy, the mechanical properties generally deteriorate with the variation in the microstructure; e.g. the precipitation of β-phase and/or decrease in solute Mg concentration in the matrix. This paper dealt with the changes in the microstructure during aging treatment at 453 K for times up to about 107 s. Variation in the solute Mg concentration was estimated by electrical resistivity measurement, X-ray diffraction and electron probe microanalysis. Precipitation of the β- and/or β′-phase was also investigated by means of microscopic strain measurement, differential scanning calorimetry and microstructural image analysis. The specimens aged for times longer than 106 s show decreases in electrical resistivity and lattice constant in relation to the formation of precipitates. Microscopic strain, which is induced by the formation of precipitate having a partially coherent interface with the matrix, shows a peak value for the aging time of about 106 s and then decreases.