Crystallization progress and soft magnetic properties of Finemet alloy with Ge addition

• The Fe71.5Si9.5Ge6B9Nb3Cu1 amorphous ribbons were produced by melt spinning technique in air.
• The crystallization activation energies of amorphous ribbons were calculated.
• MS of the as-quenched sample is higher than that of the annealed sample.

The influence of the partial substitution of Si by Ge (6 at.%) on the structure, crystallization kinetics and magnetic properties of Finemet-type alloys were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimeter (DSC) and room-temperature hysteresis loops measurements. Amorphous ribbons were heat treated at different temperatures for 1 h in a vacuum furnace to induce nanocrystallization. It was found that a homogeneous structure of α-Fe3Si structure nanocrystals with a grain size less than 15 nm embedded in an amorphous matrix was obtained within the temperature range of 510–590 °C. The crystallization activation energies calculated using Kissinger model were 331 and 356 kJ/mol for the first and the second crystallizations, respectively. The saturation magnetization of the as-quenched amorphous ribbon is 138 Am2/kg and decreases gradually with the increase of annealing temperatures from 125 Am2/kg for 510 °C to 115 Am2/kg for 590 °C.