The physical processes associated with the formation of various normal as well as metastable phases at an ion beam mixed Fe-Al interface are studied by using a novel interfacesensitive Conversion Electron Mbssbauer Spectroscopic (CEMS) technique.This technique which has been introduced and used for the first time in these investigations, is based on the deposition of a thin (less than 50 A°) layer of enriched Fe 5 7 isotope (95.45% by composition) at the interface between the aluminium substrate and a post-deposited 250A° film of natural iron (only 2.2% of Fe 57), leading to a considerably enhanced spatial selectivity of the M~ssbauer information regarding the reactions occurring at the interface.A number of samples prepared in the manner mentioned above are subjected to an argon ion bombardment at an incident ion energy of 100 keV and a dose of ≃ 2 × 1016 ions/cm2 The ion beam mixed samples are annealed at different temperatures in the range between 300°C to 600°C for twenty minutes, to provide the thermal energy for the growth of different Fex Aly phases at the interface.Conversion Electron Mössbauer Spectroscopy is employed at each stage of the ion beam processing and annealing of the samples, to characterize the phases formed. All the Mbssbauer spectra are least square fitted using the MOSFIT programme to obtain the best-fit values of Mössbauer parameters. The results indicate a substantial broadening of the Mössbauer lines for the as-implanted samples, a fact which can be attributed to the beam induced radiation damage. Subsequent annealing of the samples at different temperatures leads to annealing of damage and further to the formation of Fe3 Al and FeAl solid solution. Mössbauer spectra of the samples annealed at 500°C indicate segregation of Fe at the interface along with the formation of Fe3Al phase, while annealing at 600°C results in the formation of Fe-Al solid solution phase with traces of effectively unreacted metallic Fe. The unimplanted composites heat-treated in an identical manner do not show these features. These results which are supported by RBS measurements, are interpreted and discussed in terms of the non-equilibrium nature of the ion beam processing of the interface.