Microstructure and physical properties of mechanically alloyed Fe-Mo powder

Solid-state reactions in Fe74Mo26 powder mixture induced by mechanical alloying (MA) are followed by 57Fe Mössbauer spectroscopy supported by additional experimental methods. It is established that a bcc-Fe(Mo) solid solution with an enhanced Mo content substantially exceeding the equilibrium solubility limit, a bcc-Mo(Fe) solid solution, and an amorphous and/or highly defected phase have been formed during the MA. The mean particle size of 100 nm is obtained at the end of milling process. Surface regions of the particles are formed by the amorphous phase containing also iron grains smaller than 20 nm, as proved by transmission electron microscopy and selective area electron diffraction. A varying composition of FeMo powder samples and grain refinement are reflected in changes of hyperfine interactions and macroscopic magnetic characteristics.