An X-ray diffractometer with a monochrometer is used in the analysis of a meta-stable alloy system prepared by implanting iron ions to high doses in aluminum substrates at room temperature. The X-ray analysis of the specimen was carried out in the “as implanted” condition and after heat treatment at 400 and 500°C for 500 and 120 min, respectively. These times and temperatures were based on an earlier experiment of Rutherford backscattering of alpha particles on similar specimens, which had shown outdiffusion of the implanted iron. An effort is made in this work to study the nature of the phase transformation the alloy system undergoes during the process of outdiffusion. Earlier work on similar specimens using X-rays in the forward reflection method, the Mössbauer effect, and Rutherford backscattering experiments are used in complementing the observations made here.