Influences of Chemical Compositions and Heat Treatment on the Magnetic Properties of High Permeability Ni-Mn-Cu-Fe Alloys

In order to develop a new 70%Ni-Fe type permalloy with high permeability, a systematic investigation has been carried out on the effects of alloying elements, annealing temperature and cooling rate on the magnetic properties in Ni-Mn-Fe-Cu-Si alloys. Optimum chemical composition was found to be Ni-12at% Mn-6at% Fe-9at%Cu-2at%Si. The alloy reveals as high as 450000 of initial permeability and approximately 4mOe of coercive force after annealing at 1100°C for 2 hours followed by cooling at a rate of 1000°C/h. The dependence of magnetic properties on cooling rate is considered to result from the occurrence of proper degree of ordering as shown in Ni-Mn binary alloy by Hahn. This newly developed alloy, due to its excellent magnetic properties and good workabilities, is suitable for magnetic shielding materials.