New Nd2Fe14B-based High Performance Permanent Magnets with Improved Toughness for Propulsion

"High-performance sintered rare earth magnets are based on intermetallic compounds of SmCo5, Sm2Co17, or Nd2Fe14B. Each of these compounds is intrinsically brittle and can only be shaped by grinding, lapping, and electro-discharge machining (EDM). Evengrinding and lapping these magnets to the required dimensions often results in chipping, cracking, or fracture, leading to production losses ranging from 10 - 30%. Bonded rare earth magnets can overcome some difficulties associated with brittle behavior,however, adding a non-magnetic binder reduces magnetic performance by about 50%. Studies performed by the EEC/UDRI team during the Navy STTR Phase I program showed that a 76% improvement in the fracture toughness of sintered Nd-Fe-B magnets can beachieved by compositional modifications with little loss in magnetic performance. The objectives of the STTR Phase II program are to further increase the fracture toughness of sintered Nd2Fe14B-based permanent magnets to greater than 76% improvement ascompared with the current commercial Nd-Fe-B magnets by optimizing composition, microstructure, and processing. At the same time, the reduction in magnetic performance associated with the compositional modification is held to less than 2 - 4%. Byachieving these goals, a new type of sintered Nd-Fe-B permanent magnets combining high magnetic performance and high fracture toughness will be developed.BENEFITS: A new type of sintered Nd-Fe-B permanent magnets combining high magnetic performance andhigh fracture toughness will be developed during the Navy STTR Phase II research program. Because of the significantly improved fracture toughness (>76% improvement in comparison with conventional sintered Nd-Fe-B magnets), problems resulting from thebrittleness of the sintered magnets, such as chipping, cracking, or fracture during grinding, assembly, or operation, can be avoided or significantly reduced. Further, the improved toughness could permit both magnet manufacturers and users to shape thesemagnets by other traditional low-cost methods such as dri