Microstructure characterization of nanocrystalline Fe3C synthesized by high-energy ball milling

Carbide preparation in a conventional route requires a huge instrumentation regarding melting the metal and graphite under vacuum at a very high temperature. However, mechanical milling of powder ingredients at room temperature can easily produce nanocrystalline metal carbides. This article reports the preparation of nanocrystalline Fe3C by mechanical milling of alpha-Fe and graphite powders under inert atmosphere at room temperature. Mossbauer spectra of ball-milled powder clearly reveal that the Fe3C phase is initiated at 3 h of milling and the stoichiometric Fe3C is formed after 5 h of milling. Further milling up to 8 h results in peak-broadening of X-ray diffraction pattern of Fe3C phase. Microstructure in terms of different lattice imperfections is characterized employing Rietveld's method of structure refinement. The phase transformation kinetics studied through Rietveld method reveals that a small number of carbon atoms diffuse into alpha-Fe matrix and Fe3C phase is formed through the solid-state reaction of nanocrystalline graphite and alpha-Fe powders during ball milling. (C) 2008 Elsevier B.V. All rights reserved.