Preparation and magnetic properties for supersaturated Fe-C solid solution with nanocrystalline structure

The supersaturated solid solutions Fe1−xCx(0⩽x⩽0.9) have been prepared by mechanical alloying process. The nanocrystalline phase was formed for 0⩽x⩽0.67 and the large grain phase for 0.75⩽x⩽0.9. The large fraction of graphite volume puts off the formation of nanocrystalline phase for high carbon content. In the large grain phase, magnetization follows the simple magnetic dilution and the coercivity Hc is mainly due to the dissolution of carbon in the grain boundaries. In the nanocrystalline phase, the alloying effect of carbon is revealed by a distinct reduction of average magnetic moment. The increasing lattice constant with increasing carbon content is observed for x⩽0.5, which suggests that the high carbon concentration enhances the diffusion of carbon into the Fe lattice. It is observed the dependence of grain size on the coercivity Hc. The decrease in the mean moment per Fe atom is probably linear with the increasing carbon content for nanocrystalline phase x⩽0.5. The solubility limit of carbon in α-Fe extended by nanocrystalline phase formation is also discussed in this paper.