We report a theoretical study of microstructure, magnetic properties, and their relationship in relatively concentrated Fe-Cr alloys in both Fe- and Cr-rich regions. Annealing of initially random systems at 500° C for times of the order of 106 s substantially changes their microstructure. In both systems, solute atoms form clusters with their sizes increasing with time according to power law, with exponent being close to 0.2. For the Fe-32 at. % Cr alloy, magnetization and the Curie temperature increase with increasing annealing time and cluster size. At large simulation times, the Curie temperature approaches its value for Fe-15 at. % Cr, the concentration of completely phase-separated iron-rich alloy. For the Cr-25 at. % Fe alloy, precipitation also results in an increase of magnetization and the Curie temperature, although characteristic times are about one order of magnitude greater.