Abstract
High-performance permanent magnets based on the Nd-Fe-B ternary system can be prepared by melt-spinning of the molten alloy and subsequent pressing to full density at elevated temperature. The starting composition is always slightly rich in Nd compared to stoichiometric Nd2Fe14B in order to ensure the formation of the Nd-rich grain boundary phase. The excess Nd additions also serve to keep elemental Fe particles from precipitating but, instead, lead to unexpected precipitation within the Nd2Fe14B grains. The current research seeks to fully characterize the structure of the precipitates.Electron transparent specimens for TEM examination were prepared by mechanical grinding of thin sections cut from the hot pressed Nd0.135Fe0.815B0.05 magnets, followed by argon ion beam milling at 6 kV. Most of the samples were studied in a JEOL 1200EX STEM equipped with EDS, operating at 120 kV. A few samples were examined at higher resolution in a JEOL 200 CX TEM operated at 200 kV, employing a side entry goniometer stage and a LaB6 cathode.
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