Title :
TEM study of inhomogeneities in Nd-Fe-B sintered magnets
Author :
Jezierska, E. ; Kaszuwara, W. ; Klodas, J. ; Wojciechowski, S.
Author_Institution :
Fac. of Mater. Sci. & Eng., Warsaw Univ. of Technol., Poland
fDate :
3/1/1994 12:00:00 AM
Abstract :
Nd-Fe-B sintered magnets with a nominal composition Nd18.8 Fe73.6B6.9Al0.7 and Nd19 Fe69.8B6.4Al4.5 were prepared by conventional powder metallurgy processes and post-sintering heat treatment. Microstructure studies were performed by transmission electron microscopy (TEM) using Philips EM300 and Hitachi (200 kV). Specimens for TEM were prepared by electropolishing and ion thinning. The structure of these magnets contains following inhomogeneities nanocrystalline phase on grain boundaries and interfaces, grain boundaries without isolation of the Nd-rich phase, interface irregularities or anomalous strain contrast, low angle boundaries and coincidence boundaries between Nd2Fe14B phase and coherent interfaces. It was observed that higher Al concentration improves magnetic properties by allowing grain boundary phase to form equal thickness layer without stress concentration on the interface
Keywords :
alloying additions; aluminium alloys; boron alloys; crystal microstructure; ferromagnetic properties of substances; iron alloys; neodymium alloys; permanent magnets; sintering; transmission electron microscope examination of materials; Nd-Fe-B; Nd-Fe-B sintered magnets; Nd18.8Fe73.6B6.9Al0.7; Nd19Fe69.8B6.4Al4.5; anomalous strain contrast; coincidence boundaries; conventional powder metallurgy processes; electropolishing; grain boundaries; interface irregularities; ion thinning; low angle boundaries; magnetic properties; post-sintering heat treatment; transmission electron microscopy; Grain boundaries; Heat treatment; Iron; Magnetic field induced strain; Magnetic properties; Magnets; Microstructure; Neodymium; Powders; Transmission electron microscopy;
Journal_Title :
Magnetics, IEEE Transactions on
