Advanced Processing of Permanent Magnets

In addition to the conventional sample preparation methods, advanced processing routes may lead to better magnetic properties. On example for advanced processing of high-performance Nd-Fe-B permanent magnets is the hydrogenation disproportionation desorption and recombination (HDDR) process. This process can be employed in order to process highly anisotropic nanocrystalline Nd-Fe-B powder which can be aligned in a magnetic field and bonded with resin in order to prepare highly texture magnets [1].

Mn-based magnetic materials have been receiving much attention in the aftermath of the recent rare-earth crisis, as the rocketing prices of Nd and Dy pushed researchers to embark upon a search of alternative permanent-magnet materials containing no critical elements. Together with Mn–Al and Mn–Bi alloys, the Mn–Ga alloys are scrutinized for use as hard magnetic materials. Different advanced processing routes can be applied to the samples and in this work, we focus mainly on severe plastic deformation and magnetic field assisted processing. The obtained results indicate the strong effect of deformation and field assisted annealing on the formation of the metastable phases of the Mn-Ga binary system. With this combination of methods, we managed to obtain high coercivity values of Mn-Ga samples [2].

[1] O. Gutfleisch, K. Güth, T. G. Woodcock, and L. Schultz, Recycling Used Nd-Fe-B Sintered Magnets via a Hydrogen-Based Route to Produce Anisotropic, Resin Bonded Magnets, Advanced Energy Materials, 3 (2013) 151-155.
DOI: 10.1002/aenm.201200337

[2] S. Ener, K. Skokov, D. Karpenkov, M. Kuz'min, and O. Gutfleisch, Magnet properties of Mn70Ga30 prepared by cold rolling and magnetic field annealing, J. Magn. Magn. Mater. 382 (2015) 265-270
DOI: 10.1016/j.jmmm.2015.02.001