Abstract
Since the original discovery of Masumoto et al. that Ni–Mn alloys containing about 24% Mn or less show high permeability when subjected to a proper heat treatment, much work has been carried out so as to investigate the effects of additions of various elements on the special characters of the high-permeability alloys in the Ni–Mn system named “Nimalloy”. The series of experiments have achieved good results in producing a number of excellent magnetic alloys. It has become clear that Ni–Mn–Fe alloys should be cooled as rapid as possible and Ni–Mn–Mo alloys as slow as possible to develop their excellent magnetic properties. As in the case of Ni–Mn–Fe–Cr alloys, it was expected that Ni–Mn–Fe–Mo alloys would exhibit excellent mgnetic properties when treated at an intermediate cooling rate. A detailed investigation has confirmed that excellent magnetic alloys in the quarternary system can be produced by a moderate cooling rate at the level of furnace cooling. The highest initial permeability of 46540 has been obtained on the alloy composed of 76.88% Ni, 11.22% Mn, 4.67% Fe and 7.23% Mo which was cooled from 900°C at a rate of 400°C/hr, and the highest maximum permeability of 270000 on the alloy of 77.13% Ni, 10.66% Mn, 5.15% Fe and 7.06% Mo which was cooled from 900°C at 2800°C/hr. The latter alloy has a coercive force of 0.0019 Oe and a magnetic hysteresis loss of 0.53 erg/cm3/cycle, its electrical resistivity being 89.4 μ Ω-cm (20°C).
