Title :
Comparison of the corrosion behavior of die-upset and sintered NdFeB magnets
Author :
Ma, B.M. ; Lee, D. ; Smith, B. ; Gaiffi, S. ; Owens, B. ; Bie, H. ; Warren, G.W.
Author_Institution :
Magnequench Technol. Centre, Research Triangle Park, NC, USA
fDate :
7/1/2001 12:00:00 AM
Abstract :
Corrosion rates for sintered NdFeB magnets are compared with NdFeB magnets prepared from melt spun material (hot pressed and die upset). Corrosion rates were determined by standard electrochemical methods in 0.9 M Na2SO4, at pH 2.4 and 4.4. Autoclave tests correlated quite well with corrosion rates measured electrochemically in the more aggressive pH electrolyte. The more aggressive pH 2.4 electrolyte is more representative of the conditions occurring in the autoclave tests. The hot pressed and die upset magnets exhibit significantly lower corrosion rates than sintered magnets. The reduction in corrosion rate is probably due to smaller grain size and diminished amounts of Nd-rich material
Keywords :
boron alloys; corrosion; ferromagnetic materials; grain size; hot pressing; iron alloys; melt spinning; neodymium alloys; permanent magnets; sintering; NdFeB; NdFeB sintered magnet; autoclave test; die upset; electrochemical corrosion; electrolyte pH value; grain size; hot pressing; melt spinning; potentiodynamic polarization; Composite materials; Corrosion; Grain boundaries; Grain size; Iron; Magnetic materials; Magnets; Materials testing; Neodymium; Pressing;
Journal_Title :
Magnetics, IEEE Transactions on
