ELIMINATING DEGRADATION DURING BONDING OF GAS-ATOMIZED ND-FE-B

While significant progress has been made in improving the hard magneti c properties of Nd-Fe-B powder produced by inert gas atomization, the ability to maintain the hard magnetic properties dosing low temperatur e heating, such as when experienced during bonding, has not been previ ously demonstrated. For all alloys studied bulk oxidation was the prim ary degradation mechanism occurring at elevated temperatures (> 225 de grees C), In the rare earth rich conventional alloys, nucleation of re verse domains from defects located at or near the surface are a signif icant degradation mechanism which occurs at low temperatures (< 225 de grees C) and severely limits bonded magnet performance, In contrast, t he TiC modified alloys do not experience degradation during bonding at normal bonding temperatures (150 degrees C to 200 degrees C) due to e limination of the surface reversal degradation mechanism, This is due to the better bulk corrosion resistance resulting from the ability to process compositions with reductions in rare earth content coupled wit h an internal nanocrystalline microstructures which is similar to melt -spun ribbons.