Ion-beam irradiation can be used as a processing tool to synthesizemetastable materials. A particular case is the preparation of solidsolutions from immiscible alloys, which have been achieved for a whole rangeof systems. In this process, enhanced solute concentration is obtainedthrough the local mixing induced by each irradiation event, which ifoccurring at a high enough frequency, can outweigh demixing by thermaldiffusion. The resulting microstructure forms in far from equilibriumconditions, and theoretical results for these kind of driven alloys haveshown that novel microstructures exhibiting self-organization can develop.To test these predictions, we prepare Ag-Cu multilayered thin films that wesubject to 1 MeV Kr+-ion irradiation at temperatures ranging fromroom temperature to 225 °C, and characterize the specimens by x-raydiffraction, TEM and STEM. We observe two different phenomena occurring atdifferent length scales: On the one hand, regardless of the irradiationtemperature, grains grow under irradiation until reaching a size limited byfilm thickness (~200 nm). On the other hand, the distribution of speciesinside the grains is greatly affected by the irradiation temperature. Atintermediate temperatures, a semi-coherent decomposition is observed at ananometer scale. This nanometer-scale decomposition phenomenon appears as anevidence of patterning, and thus confirms on the possibility of usingion-beam irradiation as a route to synthesize nanostructured materials withnovel magnetic and optical properties.