The ion beam assisted deposition (IBAD) technique is utilized to study amorphization in Fe-Nb binary metal systems. The amorphous range covers a Nb fraction of approximately 34-60 at.%. The Fe-rich and Nb-rich supersaturated solid solutions of the bcc phase were obtained in Fe66Nb34 and Fe31Nb69 films, respectively In the Fe66Nb34 films. the 'amorphous --> amorphous + bcc --> bcc' evolution with increased ion beam energy front 2 to 8 keV is observed accompanying changes of film morphology. The phase formation in the IBAD process is determined by both thermodynamic and kinetic factors.