Development of Fe3C, SiC and Al4C3 compounds during mechanical alloying

Mechanical alloying process, as a solid-state technique, is a very useful method for fabrication of high melting point compounds like metal carbides and nitrides, which additionally have nanocrystalline structure with improved properties. In this work the development of several carbides including iron, aluminium and silicon carbides by the mechanical alloying process and the effect of subsequent heat treatment were investigated. Mixtures of elemental powders of Fe-C, Si-C and Al-C were mechanically alloyed, nominally at room temperature using a laboratory planetary ball mill. Structural changes of samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the aluminium carbide (Al4C3) could not be synthesized by mechanical alloying process alone, even after long milling times. A suitable subsequent heat treatment was required to allow Al-C reaction to take place kinetically. In contrast mechanical alloying of Fe-C as well as Si-C systems directly led to the formation of Fe3C and SiC carbides after sufficient milling time. In all cases the end product had a nanosized structure.