Influence of Cu Content on Structure, Thermal Stability and Magnetic Properties in Fe72-xNi8Nb4CuxSi2B14 Alloys

The effect of substitution of Fe by Cu on the crystal structure and magnetic properties of Fe72-xNi8Nb4CuxSi2B14 alloys (x = 0.6, 1.1, 1.6 at.%) in the form of ribbons was investigated. The chemical composition of the materials was established on the basis of the calculated minima of thermodynamic parameters: Gibbs free energy of amorphous phase formation Delta G(amorph) (minimum at 0.6 at.% of Cu) and Gibbs free energy of mixing Delta G(mix) (minimum at 1.6 at.% of Cu). The characteristic crystallization temperatures T-x(1onset) and T-x(1) of the alpha-iron phase together with the activation energy E-a for the as-spun samples were determined by differential scanning calorimetry (DSC) with a heating rate of 10-100 degrees C/min. In order to determine the optimal soft magnetic properties, the wound cores were subjected to a controlled isothermal annealing process in the temperature range of 340-640 degrees C for 20 min. Coercivity Hc, saturation induction Bs and core power losses at B = 1 T and frequency f = 50 Hz P-10/50 were determined for all samples. Moreover, for the samples with the lowest Hc and P-10/50, the magnetic losses were determined in a wider frequency range 50 Hz-400 kHz. The real and imaginary parts of the magnetic permeability mu ', mu '' along with the cut-off frequency were determined for the samples annealed at 360, 460, and 560 degrees C. The best soft magnetic properties (i.e., the lowest value of Hc and P-10/50) were observed for samples annealed at 460 degrees C, with Hc = 4.88-5.69 A/m, Bs = 1.18-1.24 T, P-10/50 = 0.072-0.084 W/kg, mu ' = 8350-10,630 and cutoff frequency at 8-9.3 x 10(4) Hz. The structural study of as-spun and annealed ribbons was carried out using X-ray diffraction (XRD) and a transmission electron microscope (TEM).

Automated summary

The effect of substituting Fe with Cu on the crystal structure and magnetic properties of Fe-Ni-Nb-Si-B alloys was investigated. The optimal soft magnetic properties were observed in samples annealed at 460 degrees C, with low Hc, high Bs and low core power losses, as well as high magnetic permeability. Structural studies were conducted using X-ray diffraction and transmission electron microscope.