BALL-MILLING OF FE-75-C-25 - FORMATION OF FE3C AND FE7C3

Powder mixtures of Fe-75-C-25 (both graphite and activated carbon) hav e been ball-milled in vacuum for periods of up to 285 h. X-ray diffrac tion, Mossbauer spectroscopy and thermal analysis measurements indicat e that an amorphous Fe3C-type phase is produced on short-term milling (less than 70 h), with a crystalline Fe3C being obtained on further mi lling to 140 h. This Fe3C-type phase was found to undergo partial carb on oxidation between 500 and 1000 degrees C during thermogravimetric m easurement, indicating the metastable state of this phase. The carbon- rich Fe7C3 phase was observed on extended milling of Fe75C25 (graphite ) to 285 h, in agreement with earlier findings. (C) 1997 Elsevier Scie nce S.A.