Structure, magnetic and Mössbauer studies of mechanically alloyed Fe–20wt.% Ni powders

Abstract: Fe–20wt.% Ni alloys were prepared using a planetary ball mill PM 400 from Retsch (with different milling times for Ω =400rpm, ω =800rpm) and P4 vario ball mill from Fritsch (with different milling conditions (Ω/ω), Ω and ω being the disc and the vial rotation speeds, respectively). The bcc-Fe(Ni) phase formation is identified by X-ray diffraction. The higher the shock power and the higher milling time are, the larger the bcc lattice parameter and the lower the grain size. The highest value of the coercive field is 1420A/m for Fe–20wt.% Ni (with shock mode (424rpm/100rpm) after 36h of milling), while the lowest value is 110A/m for (400rpm/800rpm) after 96h of milling. The milling performed in the friction mode favors the formation of alloys exhibiting a soft magnetic behavior for Fe–20wt.% Ni alloys. The Mössbauer spectra of the alloys recorded at 77 and at 300K differ according to the milling conditions and give relevant information on the local structure environment in relation with the nature of the mode used (friction or shock mode). [Copyright &y& Elsevier]