On the Aging and Precipitation of Al-Ag and Al-Zn Alloys

Polycrystalline specimens of Al-30wt % Ag and Al-30wt % Zn alloys, which were quenched into water from the temperature of solution heat treatment, were annealed at L.T. aging temperatures or reversion temperatures so as to make them contain zones of nearly equal radii for each alloy and various concentrations of solute element in zones. These specimens were cold rolled exactly to 50%, and then annealed at L. T. aging temperatures for varying time. The state of zones and precipitates were investigated by X-ray small-angle scattering photographs. The results obtained were as follows: (1) The precipitation ofγ'-phase began earlier in the specimens of Al-Ag alloy annealed at L. T. aging temperature before cold rolling than in those specimens annealed at reversion temperatures before cold rolling when annealed at L. T. aging temperatures after cold rolling. (2) The rate of precipitation of Zn solid solution in Al-Zn alloy did not depend upon the annealing temperature before cold rolling when cold rolled specimens were annealed at L. T. aging temperature. (3) In Al-Ag alloy, the rate of disappearance of G. P. zones at L. T. aging temperature depends mainly upon the annealing temperature before cold rolling. On the other hand, in Al-Zn alloy, the rate of disappearance of G. P. zones at L. T. aging temperature does not depened upon the annealing temperature before cold rolling. (4) These results may be explained without contradiction considering the relation of structures between matrix and precipitates and the deformation stacking faults.