High Permeability Alloys “Hardperm” in the Ni–Fe–Ta–Cr System

Measurements of the magnetic and electrical properties and hardness were made on quaternary Ni–Fe–Ta–Cr alloys which were heated in hydrogen atmosphere at 1150°C for 3 hr and then cooled at 0.75–600°C/hr from a temperature above the order-disoder transformation points. The highest values of initial permeability and maximum permeability obtainable with this alloy system were found to be 140000 and 599000 respectively for a composition of 74.08%Ni, 11.26%Fe, 14.11%Ta and 0.55%Cr when the cooling rate of 200°C/hr was applied. The alloy exhibited an electrical resistivity of 75.6 μΩ-cm, its Vickers hardness being 201. It is also shown that the alloys in this system possess very low magnetostriction constants.