Structural and thermal changes induced by mechanical alloying in a Fe–Ni based amorphous melt-spun alloy

Abstract

In this work, a Fe–Ni rich (80 at%) melt-spun amorphous alloy is obtained and mechanically alloyed under two milling conditions to obtain a powdered alloy. The morphology, structure and thermal behavior were analyzed as a function of milling time and conditions. The milling process is able to separate the amorphous phase in two Fe–Ni phases, one Fe–Ni richer than the other. From Mössbauer analysis, the Fe–Ni rich zone corresponds to a ferromagnetic phase with a hyperfine magnetic field distribution similar to an amorphous structure but with a higher (about 22%) average magnetic field. The increase on the magnetic field during the milling process provokes the shift of the main peak to higher fields, but the secondary peak remains in the same position and, in consequence, the distribution of magnetic fields becomes broader. A paramagnetic phase was found near 2 T. The thermal stability was followed by differential scanning calorimetry. Activation energies of the main crystallization transition were determined using the Kissinger analysis for the as quenched and the powdered-like materials. Slight diminution (about 10%) was found after mechanical alloying. Nevertheless, the crystallization processes has higher thermal stability than alloys directly developed by mechanical alloying.