Nanocrystallization of amorphous Fe–Si–B alloys using high current density electropulsing

Amorphous Fe–Si–B ribbons were nanocrystallized by using high current density dc electropulsing instead of the usual annealing. The microstructural changes were investigated by TEM, SAD, XRD, and Mössbauer spectral analysis. It was found that current pulsing promotes crystallization at a lower temperature than the usual annealing temperature. The primary crystallization temperatures of Metglas 2605 S-2 and Finemet were significantly lowered by pulsing. This enabled us to obtain 20–30 vol.% of single phase, α-Fe(Si) with a grain size of 15–20 nm in Metglas 2605 S-2. As a consequence, certain magnetic properties of this material are improved with respect to the as-quenched state. A preliminary interpretation is given for the phenomenon of electro-nanocrystallization.