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 (Fe100-xNix)(80)Nb4Si2B14 (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 degrees C. gamma-FeNi is formed in all alloys, while (Fe30Ni70)(80)Nb4Si2B14 also undergoes secondary crystallization at temperatures of approximately 480 degrees C to form a phase with the Cr23C6-type structure and a likely composition of Fe21Nb2B6. Toroidal losses have been measured for (Fe70Ni30)(80)Nb4SiyB16-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.