The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe_100?x Ni _x )₈₀Nb₄Si₂B₁₄ (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in all alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe₃₀Ni₇₀)₈₀Nb₄Si₂B₁₄ also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr₂₃C₆-type structure and a likely composition of Fe₂₁Nb₂B₆. Toroidal losses have been measured for (Fe₇₀Ni₃₀)₈₀Nb₄Si _y B_16?y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W_{1.0T, 400 Hz} = 0.9 W/kg and W_{1.0T, 1 kHz} = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.