Nanocrystallization by current annealing (with and without tensile stress) of Fe73.5−xNixSi13.5B9Nb3Cu1 alloy ribbons (x=5, 10, and 20)

Abstract

Microstructural ͑crystalline volume fraction and grain size͒, magnetization ͑coercive field͒, and saturation magnetostriction measurements in Fe 73.5−x Ni x Si 13.5 B 9 Nb 3 Cu 1 alloy ribbons ͑x = 5, 10, and 20͒ treated by current annealing and stress-current annealing are presented. Microstructural analysis of the treated ribbons using x-ray diffraction showed a high content of the amorphous phase in the bulk. In addition, substantial changes in the crystalline state such as grain size of the samples annealed at different conditions were observed. The alloy composition also affects greatly the grain size: increase in Ni content leads to higher values of the average grain size. The evolutions of the coercive field with the two kinds of thermal treatment were analyzed, allowing us to conclude that the addition of Ni tends to reduce the magnetic softness of the original material and that the coercivities are higher in the samples treated by stress annealing than in those treated without tensile stress. On the other hand, the saturation magnetostriction decreases with the thermal treatment, which is in agreement with the microstructural behavior ͑structural relaxation and nanocrystallization process͒, although some discrepancies are found for samples with x =5.

Effect of the Current Annealing (without and with Tensile Stress) on the Soft Magnetic Behaviour of Fe<SUB>73.5–<I>x</I></SUB>(Co<SUB>0.5</SUB>Ni<SUB>0.5</SUB>)<SUB><I>x</I></SUB>Si<SUB>13.5</SUB>B<SUB>9</SUB>Nb<SUB>3</SUB>Cu<SUB>1</SUB> Alloy Ribbons (<I>x</I> = 2.5, 5 and 10)

“…In previous works, [11][12][13][14] we have reported on the microstructural changes and the correlation with the soft magnetic behaviour in Fe-(Co or Ni)-Si-B-Nb-Cu (Co-Finemet or Ni-Finemet, respectively) amorphous alloy ribbons induced by two thermal treatments (using the Joule heating with and without tensile stress) in order to elucidate the complex magnetic behaviour which can be expected. It was analysed the effect of partial substitution of Fe atoms by Co or Ni in the classical Finemet composition on the coercive field.…”