Frequency Properties of Polymer Bonded Compacts Obtained from Ball Milled Permalloy Powders with Mo and Cu Additions

Abstract

Nanocrystalline powders from the Permalloy family, Ni₇₅Fe₂₅, Ni₇₉Fe₁₆Mo₅, and Ni₇₇Fe₁₄Cu₅Mo₄, were obtained by mechanical alloying starting from elemental powders. All compositions were milled for up to 24 h in a high-energy planetary ball mill. The powders were single phase and nanocrystalline as determined by X-ray diffraction studies, with larger flatted particle sizes for Ni₇₅Fe₂₅ (about 400 μm) and Ni₇₇Fe₁₄Cu₅Mo₄ (about 470 μm), and smaller particle sizes for Ni₇₉Fe₁₆Mo₅ (about 170 μm). The homogeneity of the samples was verified by energy-dispersive X-ray spectroscopy (EDX). Soft magnetic composites were obtained by adding 3% of Araldite to the powders, followed by compaction at 700 MPa, and then polymerization. A very good powder covering by the polymer layer was proven by EDX elementals maps. The influence of composition change on the electrical resistivity of the compacts was studied. Hysteresis measurements in static and dynamic fields of up to 10 kHz were recorded, showing the influence of composition and particle size on the compact properties.

Keywords: magnetic measurements; mechanical alloying; nanocrystalline; permalloy; polymerization.