  Both continuous and discontinuous precipitation is known to occur in CuAg
alloys. The precipitation of Ag-rich phase has been experimentally investigated
by atom probe tomography and transmission electron microscopy after ageing
treatment of Cu-5%wtAg at 440$^\circ$C during 30'. Both continuously and
discontinuously formed precipitates have been observed. The precipitates
located inside the grains exhibit two different faceted shapes: tetrahedral and
platelet-shaped precipitates. Dislocations accommodating the high misfit at the
interface between the two phases have also been evidenced. Based on these
experimental observations, we examine the thermodynamic effect of these
dislocations on the nucleation barrier and show that the peculiar shapes are
due to the interfacial anisotropy. The appropriate number of misfit
dislocations relaxes the elastic stress and lead to energetically favorable
precipitates. However, due to the large misfit between the parent and
precipitate phases, discontinuous precipitation that is often reported for CuAg
alloys can be a lower energetic path to transform the supersaturated solid
solution. We suggest that the presence of vacancy clusters may assist
intragranular nucleation and decrease
