This work deals with the microstructural properties of the Fe-30Co alloy prepared by ball milling of elemental iron and cobalt powders. The obtained mixed powder has been characterized by means of scanning electron microscope, X-ray microanalysis, laser diffraction, X-ray diffraction and microhardness measurements. X-ray line profile analysis based on the Rietveld method and adopting two different models has been used for the microstructural study. The refinement of the X-ray patterns shows that after 3 h of high energy milling the Fe(Co) is formed. The obtained Fe(Co) solid solution is characterized by body centered cubic structure with a lattice parameter a = 0.28564 +/- 0.00004 nm and an ellipsoidal crystallite and microstrain field. The dissolution of cobalt in iron matrix is accompanied by the compression of the crystalline lattice by 0.37%. The progress of milling process produces an increase of the Debye-Waller factor and the dislocation density leading to the hardening of the powder. The variation of microhardness with milling time shows a change in hardening mechanisms. (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.