Abstract
The present work was carried out so as to determine the phase diagram of Al side in the Al-Mg system with 0.5 wt%Ag by using the micrographic method, electrical resistivity measurements and differential thermal analysis.
The solid solubility curve of the α-phase in this alloy shifted to the side of appreciably higher temperatures compared with that in the binary Al-Mg alloy, indicating that the solubility of Mg in Al was decreased by the addition of 0.5 wt%Ag.
The results obtained by electron probe microanalysis and electron diffraction analysis showed that equilibrium precipitates in the alloys with 0.5 wt%Ag were mainly a ternary compound, Mg32 (Al, Ag)49-T phase.
Furthermore, the ageing behaviour of an Al-6 wt%Mg-0.5 wt%Ag alloy was studied by hardness measurements and electron microscopic observation.
The precipitates in an Al-6 wt%Mg alloy with 0.5 wt%Ag were finer and more uniformly dispersed than those in a binary Al-6 wt%Mg alloy, thus leading to a remarkable increase in age-hardening. It was considered that the acceleration of precipitation by the addition of silver was mainly caused by the effect of the increased supersaturation for precipitation of the T phase. However, seems it more reasonable to conclude that the increased supersaturation contributed greatly to the stability of G.P. zones which could act as nuclei of precipitates.
