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Title: Grain refinement in heavy rare earth element-free sintered Nd–Fe–B magnets by addition of a small amount of molybdenum

We employed a modified refractory-metal-addition method to achieve higher coercivity and remanence in heavy rare earth element (HREE)-free Nd–Fe–B sintered magnets. This process involved inducing the formation of a homogeneous secondary phase at the grain boundaries during sintering, making it possible to control the intergrain diffusion by adding small amounts of Mo, a refractory metal. To control the microstructure of the secondary phase effectively, a metal organic compound of the refractory metal was coated on the surfaces of the particles of an HREE-free Nd–Fe–B powder. The average grain size after this process was 5.60 μm, which was approximately 1.8 μm smaller than that of the HREE-free sintered Nd–Fe–B magnets (7.4 μm). The coercivity of the magnets prepared through this process could be increased from 11.88 kOe to 13.91 kOe without decreasing their remanence.
Authors:
; ; ;  [1] ;  [2]
  1. Department of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)
  2. Korea Automotive Technology Institute (KATECH), Cheonan-si 330-912 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22409963
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; APPROXIMATIONS; BORON ALLOYS; COERCIVE FORCE; DIFFUSION; GRAIN BOUNDARIES; GRAIN REFINEMENT; GRAIN SIZE; IRON ALLOYS; MAGNETIC MATERIALS; MAGNETS; MOLYBDENUM; MOLYBDENUM ADDITIONS; NEODYMIUM ALLOYS; ORGANOMETALLIC COMPOUNDS; POWDERS; SINTERING; SURFACES