Magnetic Properties of High Permeability Alloys “Hardperm” in the Ni-Fe-Nb-Ta System

Magnetic property, electrical resistivity and hardness were measured on Ni-Fe-Nb-Ta alloys containing 70.50-90.12%Ni, 5.03-19.76%Fe, 0.50-10.58%Nb and 0.52-20.50%Ta. These alloys were first heated in hydrogen atmosphere at a temperature between 1323 and 1573 K, and then cooled at various rates from a temperature above the order-disorder transformation point. The highest initial permeability of 171 mH·m−1 was obtained for an alloy containing 78.18%Ni, 11.83%Fe, 6.94%Nb and 3.05%Ta, and the highest maximum permeability 925 mH·m−1 for an alloy containing 75.26%Ni, 11.51%Fe, 3.05%Nb and 10.18%Ta when cooled at a rate of 2.22×10−1 K·s−1 after annealing at 1523 K for 7.2 ks. The alloy with the highest initial permeability exhibited the electrical resistivity of 0.732 μΩ·m and Vickers hardness of 210. The Ni-Fe-Nb-Ta alloys showed high permeability and low magnetostriction in a proper ordering state resulting from the effect of cooling.