Structural and Magnetic Characterization of High Performance Die-Upset Forged Nd-Fe-B Magnets

The processing method of anisotropic Nd-Fe-B magnets, based on rapid solidification of a molten alloy, followed by hot pressing and die-upset forging is currently well established and commonly used for the processing of high performance magnets. In this method uniaxial stress, created in an isotropic, polycrystalline alloy, leads to texture formation with the crystallographic c axis, of the tetragonal structure in each grain, being parallel, to the deformation direction (DD). However, the mechanisms leading to the anisotropic structure and accompanying processes are still not fully understood. In this study the Fe73.7Nd13.6Co6.6Ga0.6B5.5 alloy, after rapid solidification by melt spinning and hot pressing was subjected to die-upset forging with strains 30% and 65%, respectively. Systematic studies of the structure, microstructure and magnetic domain structure versus processing parameters were performed for this alloy, using magnetic measurements, transmission electron microscopy and atomic force microscopy.