The model permanent magnet based on iron-dysprosium-carbon

Transformation of Fe/sub 17/Dy/sub 2/C/sub x/ to Fe/sub 14/Dy/sub 2/C produces Fe-Dy-C alloys with intrinsic coercivities exceeding 1200 kA/m (15 kOe). After the material is crushed to produce -325 mesh (<38 mu m) particles, typically 2/3 of the coercivity remains. This improved retention of magnetic hardness is attributed to the nature of the grain boundary region, which is less vulnerable to the deformation that accompanies comminution. The phase that impedes the movement of domain walls lies in a thin grain boundary layer, has a composition which is close to that of the principal 14:2:1 phase, and is therefore presumed to be magnetic. Its structure is unknown, but is not that of a recognized binary Fe-Dy or ternary Fe-Dy-C compound. The temperature window for the formation of Fe/sub 14/Dy/sub 2/C is from 850 degrees C to below 1200 degrees C.<
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