X-ray diffraction study of nanocrystalline phases formation in metallic systems

The synthesis and structural characterization of some nanocrystalline alloys is reported in this paper. Fe-based nanocrystals, with interesting soft magnetic properties, have been obtained by crystallization of amorphous alloys. After thermal treatment of amorphous Fe73.5CU1Nb3Si13.5B9 and Fe90Zr7B3, the nanocrystalline bcc phase, with a grain size of the order of 15 nm, is embedded in the amorphous matrix. Its formation is due to the low growth rate of the crystal phase, which is related to the presence of atomic species with low diffusivity. Single fee solid solutions has been obtained by ball milling Cu and Co pure elements, which show, in equilibrium conditions, a wide immiscibility gap in solid state. The lattice parameter values, which have been followed for Cu70Co30 and Cu50Co50 as a function of milling time, indicate the occurrence of the alloying reaction. The miscibilty gap can be overcome because of the creation of a large number of defects and interfaces, which rise the free energy of the system.