Thermal and structural changes induced by mechanical alloying in melt-spun Fe-Ni based amorphous alloys

Abstract

Melt-spun Fe-Ni based amorphous ribbons were mechanically alloyed to obtain powdered-like alloys. The as-milled ribbons were characterized by differential scanning calorimetry, scanning electron microscopy with microanalysis, induction coupled plasma spectroscopy and Mössbauer spectroscopy. The increase of the rotation speed reduces the time necessary to obtain the powdered alloys. Slight contamination from milling tools and atmosphere were detected and increase with milling intensity and time. Calorimetry shows a relaxation process in all cases and a lower thermal stability of the amorphous or disordered phases with the increase in the ball to powder weight ratio. The Mössbauer HF distribution of alloys milled at 350. rpm. shows two well defined magnetic hyperfine fields, corresponding to a Fe-P based amorphous phase and to the formation of a ferromagnetic fcc Fe-Ni alloy in a disordered state. The HF distribution of alloys milled at 450. rpm. corresponds to an amorphous-like Fe-P based phase

Financial support from MICYT (projects No. MAT2000-0388 and MAT2001-0957) and DURSI (SGR2001-00190)