The Fe-Si mechanical alloying and its transformation are investigated to evaluate whether mechanical alloying is a useful process for producing Fe-Si alloy. The mechanical alloying process of Fe-Si powders is studied by SEM（ scanning electron microscopy）, EDS（energy dispersive spectrometer）and XRD（X-ray diffraction）. The results show that the ball milling process first makes tough Fe powder a lump structure and brittle Si powder a small particle, and then as the mill power increases, the tough powder of iron with a lamellar structure forms and the Si particles lies on or between the Fe lamellas. Finally, the Fe and Si powders are mechanically alloyed through atom diffusion. So the Fe and Si powders can be alloyed by 15 h ball milling at a speed of 400 r/min and with a ball-to-powder ratio of 40 ： 1. After heating at 1 243 K for 1 h, the milled powders transform to α-FeSi2, and after heating at 1 243 K for 1 h, then cooling to 1 073 K for 1 h, the milled powders transform to β-FeSi2. Therefore, the monophase α-FeSi2 or β-FeSi2 can be obtained by heat treatment of mechanically alloyed Fe-Si powders.
