Mechanical alloyed mixtures of elemental Fe and Si powders with compositions Fe_xSi_100-x (10≤X≤50) have been characterized in the as-milled condition, as well as after heat treatments. Ball-milling in an argon atmosphere first induces alloying of the elements, followed by the formation of FeSi(ε) compound in the mixture of Fe₅₀Si₅₀, and FeSi₂(β) compound in the mixture of Fe₃₀Si₇₀. Upon heating a Fe₃₀Si₇₀ mixture previously milled for 720ks, transformation to an almost single phase FeSi₂ occurs, with the exothermic reaction at around 723K. The MA powders milled for 720ks, heated to temperatures between 1173K and 1273K and air cooled, exhibited the phases. expected from the Fe-Si phase diagram. A substantial enhancement of the (Fe₂Si5(α) + ε) to β transition was observed in the MA powders of Fe₃₀S₇₀ composition in which the β phase formed from (α+ε) during furnace cooling from 1273K. This enhancement of the (α+ε) to β transition is considered to be due to the enhanced diffusion resulting from the refinement of grain sizes of the α and ε phases after MA.