SOLID-STATE REACTION INDUCED BY POST-MILLING ANNEALING IN THE FE-SI SYSTEM

We report on the far from equilibrium phase transitions induced by mechanical alloying and post-milling isothermal annealing in the Fe-Si system. Based on X-ray diffraction patterns, the influence of the mechanical alloying conditions (i.e. energy and frequency of the shocks) on the structures of the end-products were investigated. Specific attention was paid to a particular phase exhibiting some very interesting physical properties: the beta-FeSi2 crystalline phase (a semiconductor-type phase exhibiting a direct optical gap and thermoelectric power). A direct relation was found between the Fe grain size and the Fe residual strain of the as-milled Fe + Si mixture and the end product obtained by isothermal annealing.