INTECIN   20395
INSTITUTO DE TECNOLOGIAS Y CIENCIAS DE LA INGENIERIA "HILARIO FERNANDEZ LONG"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Synthesis, structure and properties of Finemet-like alloys
Autor/es:
SILVEYRA, JOSEFINA M; CREMASCHI, VICTORIA J
Lugar:
La Plata
Reunión:
Congreso; HK 2010 - Humboldt Kolleg: International Conference on Physics; 2011
Resumen:
Since the first synthesis of nanocrystalline Fe-based alloys in Fe-Si-B-Nb-Cu system in 1988 by Yoshizawa et al., a special interest has been devoted to improving the performance of the material from academic research to industry. The good soft magnetic properties of this system result in a variety of practical uses such as transformer cores, inductive devices, magnetic shielding, sensors, etc. Nanocrystalline Fe-Si-B-Nb-Cu alloys are obtained by devitrification from amorphous state and reveal an ultrafine grain structure of DO3-FeSi with grain sizes around 10-20 nm and random orientation, embedded in a ferromagnetic amorphous matrix. Due to their production inherent low thickness (~20 um) and relatively high electrical resistivity (~7.4 g/cm3), these materials exhibit excellent soft magnetic properties in a wide range of frequencies up to several hundred kHz, competing with those of Co-based amorphous alloys and MnZn ferrites. The saturation magnetization and dc coercive force are ~1 T and ~0.6 A/m, respectively. Finemet is the well-known trademark of the alloy Fe73.5Si13.5B9Nb3Cu1 and Vitroperm is the trademark of the alloy Fe73.5Si15.5B7Nb3Cu1. Effects of a partial replacement of Nb by Mo on the Finemet alloy has rarely been investigated and it was reported to maximize the magnetic permeability while it can provide cost savings because Mo is more abundant and cheaper than Nb. According to the materials science tetrahedron, the optimization of the performance of a material lies in the triangle defined by the interrelationship among its synthesis, structure and properties. In the present work the triangle synthesis-nanostructure-magnetic properties of Mo-doped Finemets is explored. The wide variety of techniques includes XRD, TEM, Mössbauer spectroscopy, Bitter technique, DSC, DTA, TGA under magnetic field, resistivity, dilatometry, magnetoresistance measurements, dc and ac magnetic measurements as well as ab initio calculations and simple balance models.