Microstructure and magnetic properties of Fe–79%Ni–4%Mo alloy fabricated by metal injection molding

Fe–79%Ni–4%Mo alloy is well known to be a soft magnetic material widely used for the magnetic head, magnetic shield, and instrumentation components because of high permeability and low coercivity. In order to realize economical mass production of minisize, complex shaped and high performance soft magnetic parts, Fe–79%Ni–4%Mo alloy was produced by metal injection molding, using carbonyl iron, carbonyl nickel and molybdenum powder as raw materials. The effects of sintering temperature and time on the microstructure and magnetic properties of the alloys were investigated. The results indicate that the magnetic properties are dependent on the microstructure. The densification and grain size of the alloys increase with increasing sintering temperature and time, facilitating the enhancement of permeability and saturation induction, as well as the decrease of the coercive force. In the case of the sintering temperature of 1320 °C for 10 h, the relative density of 97.2%, the maximum permeability of 116000, saturation induction of 0.8 T and coercive force of 1.126 A/m were achieved. Further elongation of sintering time did not bring about an increase of densification and grain size.