Surface hardening of Al by high current Fe-ion implantation

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 be Al13Fe4 and its depth profile was found to depend on the current density and dose. At a fixed dose of 3 x 10(17) Fe/cm(2), implanting with a low current density from 25 to 51 mu A/cm(2), the Al13Fe4 compound penetrated into a depth between 2500 and 4000 Angstrom. Whereas implanting with a high current density up to 101 mu A/cm(2), the Al13Fe4 compound not only be situated in a 1000 Angstrom surface layer, but also extended into a deep region when the dose was increased to 1 x 10(18) Fe/cm(2). Another dual implantation was conducted with two different current densities and it resulted in a modified region of 4500 Angstrom thick with a high concentrated Al13Fe4 compound in a 1000 Angstrom surface layer. Accordingly, the microhardness of the implantation treated Al films was considerably increased. The formation of the hardening phase of Al13Fe4 compound 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. (C) 1997 American Institute of Physics.