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

• High-performance Fe–79%Ni–4%Mo alloy was produced by metal injection molding.
• The magnetic properties were found to be closely related to density and grain size.
• The sintering parameters of Fe–79%Ni–4%Mo alloy were optimized.

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.

The figure shows the effect of sintering time on the relative density and magnetic properties at 1320 °C. It can be seen that the relative density, saturation induction and maximum permeability increase while the coercive force decreases with the elongation of sintering time. Relative density increases significantly in the sintering time range of 2–8 h and maximum permeability increases quickly when the sintering time increases from 2 h to 10 h. It is noted that the density keeps almost the same after being sintered for more than 8 h, but the maximum permeability shows noticeable increase.Figure optionsDownload as PowerPoint slide