Structure and magnetic properties of Fe1−x C x , solid solution prepared by mechanical alloying

Abstract

Supersaturated solid solutions Fe1−x C x (0⩽x⩽0.9) of wide composition range have been prepared by mechanical alloying process. Nanocrystalline phase was formed for 0⩽x⩽0.67 and a large grain phase for 0.75⩽x⩽0.9. The large fraction of graphite volume puts off formation of nanocrystalline phase for high carbon content. In the large grain phase, magnetization follows simple magnetic dilution, and coercivity H c is mainly due to dissolution of carbon at 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 a;$0.5, suggesting that the high carbon concentration may enhance diffusion of carbon into the Fe lattice. It shows a discontinuity in the H c variation with a grain size D of nanocrystalline phase. For small grain D below the critical value, H c increases with D. For a large grain D, H c decreases with increasing D. The solubility limit of carbon in a-Fe extended by nanocrystalline phase formation is discussed.