The kinetics of discontinuous precipitation and dissolution of the cel
lular precipitate have been studied in Cu-3 at.% Ag and Cu-4 at.% Ag a
lloys. The growth rates of the cells were measured using optical micro
scopy. The interlamellar spacings of the primary cells and composition
s of the depleted matrix were measured using scanning electron microsc
ope and X-ray diffraction, respectively. The Cu-Ag alloys were observe
d to decompose into a lamellar structure consisting, of alternate lame
llae of the alpha (Cu-rich) and beta (Ag-rich) phases when a solid sol
ution of the alloy was aged below the solvus temperature. The rod shap
ed morphology of the beta phase dispersed in the matrix of alpha was o
bserved at all temperatures. The primary cell growth data were analyse
d using the theories of Cahn, Hillert, Sundquist, Turnbull and Peterma
nn and Hornbogen. From the diffusivity values, it has been shown that
the growth of primary cells occurs by the diffusion of Ag along the gr
ain boundaries. The results are consistent with the diffusivity values
reported in the literature in the same temperature range. The discont
inuous dissolution of the primary cells occurred above the solvus temp
erature as well as 30-40 K below it. The dissolution occurred primaril
y at the prior positions of grain boundaries as well as at the primary
cells intersection, at least in the initial stages of dissolution. Th
e discontinuous dissolution occurred by the diffusion of Ag along the
interface boundary between the primary and dissolution cells. The diff
usivity and mobility values obtained during dissolution are one order
of magnitude smaller than those obtained for the discontinuous precipi
tation. This has been explained by volume diffusion ahead of the inter
face and not all of the free energy being used to drive the interface
boundary. (C) 1998 Canadian Institute of Mining and Metallurgy. Publis
hed by Elsevier Science Ltd. All rights reserved.