Comparison of Fe-Ni based alloys prepared by ball milling and rapid solidification

Abstract

Mechanical alloying (MA) and rapid solidification (RS) are two important routes to obtain amorphous alloys. An Fe-Ni based metal-metalloid alloy (Fe 50Ni30P14Si6) prepared by these two different processing routes was studied by differential scanning calorimetry, scanning electron microscopy with microanalysis, inductive coupled plasma, X-ray diffraction (XRD) and transmission Mössbauer spectroscopy (TMS). The results were compared with that obtained from other Fe-Ni based alloys of similar compositions. The structural analyses show that the materials obtained by mechanical alloying are not completely disordered after 40 h of milling whereas fully amorphous alloys were obtained by rapid solidification. TMS analyses show that, independent of the composition, after milling for 40 h, about 7% of the Fe remains unreacted. Furthermore, the thermal stability of mechanically alloyed samples is lower than that of the analogous material prepared by rapid solidification. In the MA alloys, a broad exothermic process associated to structural relaxation begins at low temperature. XRD patterns of crystallized alloys indicate that the crystallization products are bcc(Fe,Ni), fcc(Ni,Fe), and (Fe,Ni)-phosphides and -silicides