Interdiffusion of Fe and B trilayer specimens during 1-MeV Kr+ bombardment was studied using Rutherford backscattering and electron microscopy. The square of the interdiffusion distance during mixing at 300°C was found to depend linearly on the irradiation dose. Arrhenius behavior with an apparent activation enthalpy of 0.7 eV was observed for the mixing between 200 and 500°C. Electron microscopy of ion-beam mixed multilayer specimens revealed that two crystalline compounds, Fe2B and Fe3B, formed during bombardment at 450°C, while two different amorphous Fe/B phases formed at 300°C. Substantially improved adhesion and reduced friction were observed for Fe/B multilayers ion-beam mixed onto M50 steel substrates at 450°C.