Composite Compacts of Fe/Fe3O4 Type Obtained by Mechanical Milling-Sintering-Annealing Route

Abstract

Fe/Fe2O3composite powders were obtained by mechanical milling of iron and hematite up to 120 minutes in a high energy planetary ball mill. The particles size decreases by mechanical milling upon the formation of the Fe/Fe2O3composite particles. After 120 minutes of milling the median particles size is at 7.2 μm. The Fe/Fe3O4type composite were obtained by reactive sintering in argon atmosphere at 1100 °C of the Fe/Fe2O3composite powders milled for 60 and 120 minutes. After sintering a FeO-wüstite residual phase is formed and this phase is eliminated by applying a subsequent annealing at a temperature of 550 °C. The sintered compact before and after annealing is composed by a quasi-continuous iron matrix in which are embedded iron oxides clusters (Fe3O4and FeO before annealing and Fe3O4after annealing). The iron oxide clusters are analogous with the Widmanstatten structure observed in steels before and after annealing. The materials have been investigated using laser particle size analysis, optical microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray diffraction.