Antimony/aluminium films in bilayer and multilayer geometries were irradiated at liquid‐nitrogen temperature with 50–900 keV ion beams ranging in mass from20Ne to208Pb. Depth profiling of the element concentrations was carried out via Rutherford backscattering spectroscopy. The formation of intermetallic phases and phase segregation was analyzed by means of x‐ray diffraction, cross‐section transmission electron microscopy, and scanning electron microscopy. From the low‐dose irradiation data, the mixing rateskwere obtained and found to depend linearly on the energy densityFDdeposited at the interface. The mixing efficiency of Sb/Al bilayers,k/FD=296(30) A˚5/eV, supports the local thermal spike model. After high‐fluence irradiations of Sb/Al bilayers with 550 keV Xe++ions, a reacted layer of crystalline SbAl (B3phase) at the interface was observed. Sb/Al multilayers irradiated with 900 keV Xe++ions were found to become amorphous. Phase formation was studied as a function of the ion fluence, irradiation energy, and ion mass, and was found to start at that fluence, where cracking and shrinking of the Sb top layer and an increase of the sputtering yield were also observed. ©1995 American Institute of Physics.