Ion-beam-assisted phase transformation in the Fe± N system has been studied in Fe samples implanted with N. By bombarding with Ar ions at temperatures in the 140 ë C< T < 420 ë C range, the e -Fe2N ! e -Fe2+xN + e -Fe3.2N and e -Fe 3.2 N + g 0 -Fe 4 N phase transformations were induced. The ion-assisted phase transformations were studied as a function of ® rstly the temperature of the substrate, secondly the initial N concentration and thirdly the irradiation time.The results of the experiments show that the concomitant use of ion bombardment and temperature induces a given phase transformation at a temperature that is typically 40± 50 ë C lower than that required for thermal annealing alone.