Fabrication of FINEMET bulk alloy from amorphous powders by spark plasma sintering

Finemet bulk soft magnetic alloy was fabricated by spark plasma sintering of the milled ribbons. The amorphous melt-spun ribbons were milled for 36min by high energy vibrational mill and then sieved to separate particles smaller than 125μm. The size distribution of particles was determined by a laser diffraction particle size analyzer. Spark plasma sintering was carried out at super-cooled liquid region for short times of 7 and 21min. The structure of bulk samples was characterized using X-ray diffraction, scanning electron microscopy, differential scanning calorimetry and transmission electron microscopy techniques. The magnetization and coercivity of samples were measured using SQUID magnetometry. The results indicated that during sintering the Fe(Si) phase with grain size of 9nm forms in the amorphous matrix. The amount of Fe(Si) phase was calculated as 84wt.% in the sample consolidated from fully amorphous powder for 7min. The magnetization and coercivity of this sample was measured as 122.29emug−1 and 123Am−1, respectively. The relative density of consolidated samples for 7 and 21min was reached to 96 and ~97% of theoretical density, respectively. Recording the punch displacement with respect to the time showed that the particles rearrangement and viscous flow with activation energy of 23.4kJmol−1 were the main mechanisms of densification at the first and second stages of densification, respectively.