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magnetic materials

permanent magnets based on intermetallic alloys

In the field of intermetallic alloys based on Sm-Co we investigated the influence of basic composition and processing parameters on the final magnetic properties of powders obtained by mechanical alloying. We improved the Mr/Ms values to 0,69 and retained high coercivity. The improved properties were attributed to the exchange coupling between the hard magnetic SmCo
5 phase and the soft magnetic Co.

The main goal in the preparation of anisotropic nanocrystalline Nd-Fe-B powders as a material for bonded magnets was to optimise the basic alloy's composition and processing parameters, with the final goal to achieve optimum magnetic properties of nanocrystalline powders prepared by HDDR processing (Figure)

HDDR-processed powders are isotropic, and our final task was to achieve anisotropic magnets by changing the composition with various additives and by changing the processing conditions.

SEM image of HDDR-processed Nd
powder at 400 an 40.000 magnification

The anisotropy of HDDR-processed powders enables a higher remanence (Br) simultaneously with a high coercivity. Nanocrystalline powders, which were prepared with the optimised composition and with the optimum processing route, were 87% anisotropic and allowed us to prepare bonded magnets with Br = 0.9 T. The highest coercivity achieved was 12.8 kOe (1025 kA/M).
In the Sm-Fe-Ta-N system we studied the influence of the basic composition and the preparation method on the phase composition and final magnetic properties. We found that a small amount of Ta additive has an important influence on the microstructure and the magnetic properties of the basic alloy (EU Patent). Furthermore, we discovered that the disproportionation stage in the HDDR processing is also influenced by the addition of Ta.

comments & suggestions to:  sanja fidler