Surface modification of Al was studied by high current Fe-ion implantation using a metal vapor vacuum arc ion source. In the implantation process, two parameters were adjusted, that is, current density and ion dose, corresponding to varying the temperature and time for growing surface Fe-aluminide compound. The major hardening phase was identified to beAl13Fe4and its depth profile was found to depend on the current density and dose. At a fixed dose of3×1017 Fe/cm2,implanting with a low current density from 25 to51 &mgr;A/cm2,theAl13Fe4compound penetrated into a depth between 2500 and 4000 Å. Whereas implanting with a high current density up to101 &mgr;A/cm2,theAl13Fe4compound not only be situated in a 1000 Å surface layer, but also extended into a deep region when the dose was increased to1×1018 Fe/cm2.Another dual implantation was conducted with two different current densities and it resulted in a modified region of 4500 Å thick with a high concentratedAl13Fe4compound in a 1000 Å surface layer. Accordingly, the microhardness of the implantation treated Al films was considerably increased. The formation of the hardening phase ofAl13Fe4compound was responsible for the improvement of the surface mechanical property and was discussed in terms of temperature rise, irradiation time, and radiation-enhanced diffusion in the process of implantation. ©1997 American Institute of Physics.