Mössbauer and x-ray study of mechanically alloyed Fe–Ni alloys around the Invarcomposition

Abstract

Fe100−xNix powders(22.5≤x≤40 at.%)mechanically alloyed (MA) for 10 h were characterized by x-ray diffraction (XRD) and transmission57Fe Mössbauer spectrometry (TMS). In all of this composition range, the nanostructured alloysconsist of two crystalline phases, body-centred cubic (BCC) and face-centred cubic (FCC).The Mössbauer spectra were fitted by means of a new fitting model involving two hyperfinemagnetic field distributions (HMFDs), and a narrow singlet. One HMFD corresponds tothe ferromagnetic BCC grains (tetrataenite), and the other to the ferromagnetic FCCgrains (taenite), and the narrow singlet to paramagnetic FCC grains (antitaenite orsuperparamagnetic FCC grains). The Ni content dependence of the hyperfine field at57Fe nuclei of the FCC phase gives evidence for some jump at about 32.5 at.% Ni, attributed toInvar anomaly.