Effect of Nd content on the microstructure and coercivity of hot-deformed Nd-Fe-B permanent magnets

The microstructure of hot-deformed Nd-Fe-B permanent magnets with different Nd contents was investigated in order to correlate them with the hard magnetic properties. A thick distinct Nd-rich grain boundary (GB) layer was observed in a high Nd content sample by scanning electron microscopy and transmission electron microscopy. Three-dimensional atom probe results showed a significant increase in the Nd content in the GB as the overall Nd content in the alloy increased. We found a clear correlation between the Nd concentration in the GB layer and the coercivity. The mechanism of the coercivity increase is discussed based on the microstructure characterization and micromagnetic simulation results. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.