High Magnetic Permeability Alloys Hardperm in the Ni–Fe–Ta–Mo System

Abstract

Ni–Fe–Ta–Mo alloys were heated in hydrogen atmosphere at 1150°C for 3 hr and then cooled at rates of 1400∼0.75°C/hr from a temperature above their order-disorder transformation points. The highest initial permeability is 120000 measured on the alloy of 74.35%Ni, 11.35%Fe, 13.85%Ta and 0.45%Mo cooled at the rate of 300°C/hr, and the highest maximum permeability is 610000 on the alloy of 74.20%Ni, 11.22%Fe, 13.96%Ta and 0.62%Mo cooled at 240°C/hr. The alloy with the highest initial permeability exhibited an electrical resistivity of 69.7 μΩ-cm, with Vickers hardness 199. The high permeability of the Ni–Fe–Ta–Mo alloys is largely due to the effective contributions of high-temperature heat treatments in hydrogen atmosphere to the compositional homogeneity, impurity removal, together with the low values of magnetostriction and crystal magnetic anisotropy in a proper state of ordering.