Cu-Cr alloys, irradiated with a low-energy, high-current electron beam, are analyzed by high-resolution secondary ion mass spectrometry. Mass spectra and images of Cu+ and Cr+ surface distributions finely reveal the regions enriched in Cu and Cr. For electron beam energies above a threshold value, the formation of a non-equilibrium Cu1-xCrx solid solution, extending over submicrometer areas is highlighted for the first time. A discussion of the process leading to Cu1-xCrx formation is given. (c) 2005 Elsevier B.V. All rights reserved.