X-Ray Study on Aging and Precipitation of Deformed Al-Ag Alloy

Abstract

Polycrystalline specimens of Al-30 wt%Ag alloy, which were quenched into water from 540°C, were annealed at L.T. aging temperature or reversion temperature so as to make them contain zones of various radii and concentrations. These specimens were cold-rolled exactly to 50%, and then annealed at 150°C for varying time. The state of zones and γ′-precipitates were investigated by X-ray small-angle scattering photographs. The results obtained were as follows: (1) The precipitation of γ′-phase during annealing at 150°C, begins very earlier in these specimens than in the specimens cold-rolled immediately after quenching. (2) The precipitation of γ′-phase begins earlier in the specimens annealed at L.T. aging temperature than in the specimens annealed at reversion temperature. (3) At 150°C the rate of disappearance of zones depends mainly upon their concentration rather than on their radius. The deformed zones of high concentration disappear earlier than the deformed zones of low concentration during the annealing. (4) The deformed, dilute zones become more concentrated before the precipitation of γ′-phase. (5) These results may be explained without contradiction considering that the stacking faults formed by cold working behave as the nuclei of γ′-precipitates.