| Popis: |
The mechanical alloying process has been used to synthesise the nanocrystalline Fe60Al35Mg5 ( wt % )powders in a high energy planetary ball-mill Retsch PM 400. The evolution structural, microstructural, morphological and magnetic properties of ball-milled powders at different milling times (t variation from 0 to 32 h) were investigated by X-ray diffraction using the MAUD program which is based on the Rietveld method, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) and the vibrating sample magnetometer (VSM). The XRD results reveal the formation of a bcc-Fe (Al, Mg) solid solution after 8 h of milling possessing a lattice parameter of 0,2895nm after 32 h of milling. It is also observed a refinement of the grain size which reaches 18,75 nm, and an increase in the microstrain after 32 hours of milling. Morphological evolution of the powder particles of the preceding mixture with the increase of the milling time, shows the coexistence of larger and fine particles at the beginning of the milling process linked to the competition of the phenomena of fractures and welding. A more or less homogeneous distribution of the particle shape is observed after 32 hours of milling. The elemental maps of Fe , Al and Mg done with EDX experiments confirmed the results found by XRD about the evolution of the alloy formation. Magnetic measurements of the milled Fe60Al35Mg5 ( wt % ) powder mixture exhibit a soft ferromagnetic character where the magnetic parameters are found to be very sensitive to the milling time mainly due to the particle size refinement as well as the formation of the solid solutions. After 32 hours of milling, the evolution of the saturation magnetisation (MS), coercive field (HC) remanent magnetisation (Mr) and squareness ratio (Mr/Ms) derived from the hysteresis curves are discussed as a function of milling time. |
