High Magnetic Permeability Alloys “Hardperm” in the Ni–Fe–Nb–Mo System

Ni–Fe–Nb–Mo alloys which had been heated in H2 atmosphere at 1150°C 3 hr were cooled at various rates from a temperature above their order-disorder transformation points. The alloy consisting of 80.12%Ni, 11.42%Fe, 6.92%Nb and 1.54%Mo exhibited the highest initial permeability of 103000 when subjected to cooling at the rate of 50°C/hr. Also, this alloy showed an electrical resistivity of 75.3 μΩ-cm and 199 Vickers hardness. On the other hand, the alloy of 80.19%Ni, 10.71%Fe, 8.10%Nb and 1.00%Mo exhibited the highest maximum permeability of 434000 when cooled at the rate of 70°C/hr. An outstanding feature of the high permeability alloys in this system is a low value of saturation magnetostriction constant.