Magnetic and Electrical Properties of Iron-Nickel Alloys

Part 1. This investigation was undertaken to determine whether any iron-nickel alloys could be found having a higher saturation value than pure iron. Alloys were prepared containing 0-100 per cent Ni. Pure Fe-Ni alloys do not forge readily, and to make them forgeable it is necessary to add alloying elements like Mn or Ti. The results show that the saturation value decreases slowly with increase in Ni content up to 20 per cent Ni; then rapidly to 30 per cent; again rises rapidly to 50 per cent and falls off gradually toward 100 per cent Ni. At no point does it exceed that of pure iron. For values of H between 100 and 400 the permeability is about 5 per cent higher for 6 to 8 per cent Ni than for pure iron, but this advantage is offset by the large increases in hysteresis loss. Alloys containing 35 to 70 per cent Ni have high permeability at low and medium densities and low hysteresis loss, the highest permeability occurring for 50 per cent. 30 to 50 per cent alloys are characterized by a nearly straight line B-H curve from the origin to B = 2000 to 4000 gausses and also by low retentivity and coercive force, properties which are of value in connection with certain electromagnetic meters. Part II. Previous investigations on commercial iron-nickel alloys have shown that 25 to 35 per cent alloys have irreversible magnetic and electrical transformation points occurring below ordinary temperatures.