Effect of Cr and Ni on phase formation in a mechanically synthesized nanocomposite based on Fe$_{75}$C$_{25}$

The formation and doping of phases during mechanical synthesis followed by annealing in the (Fe$_{0.80}$Cr$_{0.05}$Ni$_{0.15}$)$_{75}$C$_{25}$ alloy are studied by the method of X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. It is shown that after mechanical synthesis, the nanocomposite contains mainly two phases (amorphous phase and cementite A). During annealing, as a result of crystallization of the amorphous phase, cementite B is formed, in which the nickel concentration is higher than in mechanically synthesized cementite A. Upon an increase in the annealing temperature, austenite with a nonuniform nickel concentration is formed. The Curie temperature of such austenite reaches 500$^\circ$C. It is established that cementite in mechanically synthesized nanocomposite (Fe,Cr,Ni)$_{75}$C$_{25}$ has a higher stability to temperature variations than mechanically synthesized composite (Fe,Ni)$_{75}$C$_{25}$.