Magnetic properties of nanocrystalline Fe_~60 Cr_~40 powders prepared by mechanical alloying in vacuum and air were investigated by utilizing the measurements of magnetization, X-ray diffraction, and ~ ~57 Fe Mssbauer spectrum. The results show that the Fe_~60 Cr_~40 powders keep the bcc structure during milling in air and vacuum. The saturation magnetization of the Fe_~60 Cr_~40 powders milled in vacuum and air decreases with the increase of the milling time up to 45 h. The decrease of saturation magnetization of the Fe_~60 Cr_~40 powders milled in vacuum is due to the formation of Fe-Cr solid solution, while in air it is due to the formation of paramagnetic disorder structure and solid solution. Magnetic properties of nanocrystalline Fe_ ~ 60 Cr_ ~ 40 powders prepared by mechanical alloying in vacuum and air were investigated by utilizing the measurements of magnetization, X-ray diffraction, and ~ 57 Fe Mssbauer spectrum. The results show that the Fe_ ~ The saturation magnetization of the Fe_ ~ 60 Cr_ ~ 40 powders milled in vacuum and air decreases with the increase of the milling time up to 45 h. The decrease of saturation magnetization of the Fe_ ~ 60 Cr_ ~ 40 powders milled in vacuum is due to the formation of Fe-Cr solid solution, while in air it is due to the formation of paramagnetic disorder structure and solid solution.