The effects of the pressing step on the microstructure and aging of NdFeB bonded magnets

Author(s)

Perigo, E. A. ^[1] ; de Campos, M. F. ^[2] ; Faria, R. N. ^[3] ; Landgraf, F. J. G. ^{[1, 4]}

Affiliation

^[1] Inst Technol Res IPT, BR-05508901 Sao Paulo - Brazil

^[2] EEIMVR Fed Fluminense Univ, BR-27255125 Volta Redonda, RJ - Brazil

^[3] Nucl & Energy Res Inst IPEN, BR-05508000 Sao Paulo - Brazil

^[4] Univ Sao Paulo, BR-05508901 Sao Paulo - Brazil

• Document type: Journal article
• Source: Powder Technology; v. 224, p. 291-296, JUL 2012.
• Web of Science Citations: 10

Abstract

The effects of the compaction step on the (micro)structural features and aging behavior of polymer coated NdFeB-based bonded magnets is reported. Due to the fracture of the material during pressing, it is estimated an increase of at least 14% in the particles' area which is not coated. Such uncoated surfaces, when exposed to the environment, reduce the magnetic performance of the magnets aged/cured in air by 19% in the conditions evaluated in this investigation. Furthermore, XRD results interpreted by Rietveld analyses show a lattice parameter change in the tetragonal structure of the hard magnetic phase after pressing. Such change varies as a function of the height of the compacted part and it is ascribed to macro-elastic stress arising from the pressure distribution in the magnet. An aging/curing step during 24 h is able to relief such macro-elastic stress. (C) 2012 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 10/08018-8 - Reprocessing of commercial REFeB (RE = Nd or Pr) sintered magnets for preparation of bonded magnets and semi-hard magnetic compounds using hydrogen
• Grantee: Élio Alberto Périgo
• Support Opportunities: Scholarships in Brazil - Post-Doctoral