Structural, Microstructural and Magnetic Characterizations of Mechanically Alloyed Fe65Si20Cr15 Powders Mixture
Résumé
Nanostructured Fe65Si20Cr15 powders were prepared by mechanical alloying in a planetary ball mill. Morphological, microstructural, structural, and magnetic characterizations of the milled powders were investigated by scanning electron microscopy, X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometer. A mixture of substitutional bcc Fe(Si) (˜29 nm) and bcc Cr(Si) (˜45 nm) is obtained after 3 h of milling. Upon prolonged milling, all the as-milled powders exhibit non-equilibrium α-Fe(Si,Cr) solid solution with an average crystallite size of 19–23 nm. The lattice parameter decreases initially up to 3 h and then increases with further increase in milling time due to dissolution of Cr and Si into Fe host lattice. The variation of microstructural parameters such as average crystallite size, r.m.s. microstrain, static Debye–Waller parameter, and dislocation density as a function of milling time show good correlations. Mössbauer spectra of the milled powders, recorded at room temperature, reveal the decrease of the average hyperfine field suggesting a random distribution of atoms during milling and point out the formation of the disordered bcc Fe(Si,Cr) solid solution. After 15 h of milling, the coercivity and magnetization values are 81.7 Oe and 120.3 emu/g, respectively.