Nickel-doped nanostructured Fe₇₀Al₃₀ alloys: The role of Ni on the microstructure and the evolution of hyperfine and magnetic properties

We have investigated the effect of the Nickel concentration on the crystal structure and microstructure, as well as on the hyperfine and magnetic properties of nanostructured (Fe0.7Al0.3)(100-x)Ni-x powders (x = 0, 5, 10 and 15 at.%) fabricated by mechanical alloying. After 72 h of milling, all the Fe(Al, Ni) samples are single-phase disordered solid solutions with body centred cubic crystal structure. A progressive reduction of the lattice parameter value from 2.9084 angstrom for the Ni-free FeAl binary alloy down to 2.8897 angstrom for the x = 15 ternary compound is observed. The mean grain size of the nanocrystals also diminishes down to c.a. 20 nm as the Ni concentration is increased, whereas the mechanically-induced microstrain remains almost constant at around 0.5%. The magnetic measurements show a ferromagnetic character of all the samples at room temperature with a slight decrease of both saturation magnetization and coercivity as the Ni concentration rises. The fit of Mossbauer spectra collected at room temperature gives an almost constant value (around 26 T) for the mean hyperfine magnetic field, (T). Hence, the addition of Ni to Fe (Ni,Al) solid solution has not a clear influence on the value of , although the hyperfine field distributions suggest somewhat different local environments of Fe atoms. (C) 2020 Elsevier B.V. All rights reserved.