Properties of High Magnetic Permeability Alloys Hardperm in the Ni-Fe-Ta-Mo System

Ni-Fe-Ta-Mo alloys were heated in hydrogen atmosphere at 1150°C for 3 hr and then cooled at rates of 0.75∼1400°C/hr from a temperature above order-disorder transformation point. The highest initial permeability of 120000 are obtained for 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 of 610000 for 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 the electrical resistivity of 69.7 μΩ-cm, its Vickers hardness being 199. The high permeability Ni-Fe-Ta-Mo alloys showed the very low values of magnetostriction constant in a proper state of ordering.